Location, Construction 



and 



Maintenance of Roads 



GOODEII. 




Class 
Book.. 



i_J^5 



.^ (c 



-{) 



CQPmiGm DEPOSIT. 



The Location, Construction 
and Maintenance of Roads 



BY 



JOHN M. GOODELL 



Reprinted from 
GOOD ROADS YEAR BOOK 

1917 




NEW YORK 

D. VAN NOSTRAND COMPANY 

25 PARK PLACE 
1918 



""^^/^s- 

'^(o 



Copyright 1917 

BY 

American Highway Association 
Copyright 1918 

BY 

D. Van Nostrand Company 



OCT 21 1918 



COMPOSED AND PRINTED AT THE 

WAVERLY PRESS 

Bt the Williams & Wilkins Company 

Baltimore, U. S. A. 



'^Gl.A50B250 



Ave I \^' 






PREFACE 

In the summer of 1916, several State highway engineers re- 
ported to the American Highway Association that there was 
need of a concise explanation of the best current practice in locat- 
ing, constructing and maintaining country roads, not combined 
with information about city pavements. It was found by these 
engineers that the information in many excellent engineering 
treatises proved confusing to rural road officials because they 
did not have sufficient technical knowledge to draw a line be- 
tween what was applicable to country highways and what was 
restricted to urban conditions. Inquiry showed that such an 
outline of road-building would be welcomed by the road officials 
of other States, and the preparation of this book was accordingly 
begun. 

Highway engineers in all parts of the country generously con- 
tributed material and advice. Special attention was paid to 
ascertaining reasons for unusual methods, in order to avoid the 
publication of anything useful only in restricted locaUties and 
possibly leading to trouble if tried generally. The purpose was 
to furnish information of a national value rather than an expres- 
sion of the views of a few individuals, who inevitably have per- 
sonal preferences and prejudices. As each section was finished 
it was submitted for criticism to engineers or chemists with 
special knowledge of the subjects discussed, and most of the chap- 
ters formed by combining these revised sections were sent out 
to other engineers for further criticism. Some of the chapters 
were revised a number of times before they were finally ap- 
proved. As a consequence, although my name appears as the 
author on the title page, the book is rather the product of the 
cooperation of over fifty of the leading American highway engi- 
neers and the patient and intelligent handling of the details of 
the work by Miss Isabelle Stockett, at the time chief clerk of the 
American Highway Association. 

This book appeared originally as Part II of the 1917 Good 
Roads Year Book. Its wide cu-culation, the many references to 
it in technical journals, and its use as a textbook by engineering 
colleges, indicating that the volume had won a distinct position 
in technical literature, led the Directors of the American High- 
way Association to assign the copyright to the D. Van Nostrand 
Company, when the Association was dissolved a few days ago. 
By this action the results of the cooperative labors of so many 
specialists will remain available to the public. 

ill 



IV PREFACE 

Added to the text as it appeared in the Good Roads Year 
Book is a chapter on the reasons for improving roads. This is 
part of a ''good roads manual" for public officials, not techni- 
cally educated, which had considerable circulation in manu- 
script form among road commissioners applying to the American 
Highway Association for such information. It is printed here 
as a concise justification of the expenditure of public funds for 
road improvements, a subject which highway engineers must 
frequently discuss at pubhc meetings. 

John M. Goodell. 

Upper Montclair, N. J., March, 1918. 



CONTENTS 

Location, Grades, Widths and Cross-Sections of Rural Roads 1 

Regulations of the California Highway Commission Regarding Surveys 
and Plans 12 

Drainage, Culverts and Bridges 19 

Earth and Sand-Clay Roads 37 

Gravel Roads 51 

Water-Bound Macadam Roads 64 

Road-Building Rocks 75 

Concrete Roads 90 

Standard Specifications for Portland Cement 107 

Petroleum and Residuums 109 

Asphalt and Native Solid Bitumens 117 

Asphaltic Materials for Roads 124 

Tar and Tar Products 132 

Bituminous Roads 138 

Bituminous Surface Applications 150 

Brick Roads 157 

A Brick Pavement on a One-inch Concrete Base 178 

Highway Bonds 180 

Resistance of Roads to Traction 189 

Rural Public Roads in the United States 192 

Money Spent on Roads in the United States 193 

Extent of Surfaced Roads in the United States 194 

Motor Car Statistics 195 

Vitrified Paving Brick Production 196 

Broken Stone Production 198 

Gravel and Paving Sand Production 199 

The Reasons for Improving Roads 200 

Manufacturers and Constructors Cards 215 



LOCATION, GRADES, WIDTHS AND CROSS- 
SECTIONS OF RURAL ROADS 

The improvement of any road or system of roads must begin 
with a study of its location and grades, for unimproved roads 
are often bad in both respects. The purpose of relocation is to 
enable the road to carry the anticipated traffic with the least 
effort and loss of time. It is impracticable to relocate all roads 
and improve their grades at the present time, and highway offi- 
cials must be satisfied with gradually ehminating or at least 
reducing the defective conditions. In order to carry on this 
work efficiently, however, the entire system of roads under a 
board or commission must be studied as a whole, so that the 
whole body of taxpayers may be benefited as uniformly as 
practicable by the work done annually. The work should be 
planned in a broad way several years in advance, if possible, for 
it is only in this way that the needs of all parts of the district can 
be met without favor or prejudice. This is particularly important 
where the needs are great, the road fimds meager, and property 
has been developed along locations where roads should never have 
been laid out. The situation in such cases has been summed up 
as follows by W. S. Keller, State highway engineer of Alabama: 

The genuine bad roads cannot be maintained for the reason that they 
have never been constructed. The great amount of work necessary to 
keep them in passable condition disheartens the man who is by law com- 
pelled to work them. Until these roads are relocated, avoiding heavy grades 
and marshy bottoms, sharp angles and useless twists, and are graded so 
they will have good drainage, we may expect them to be bad. 

Location. — It is evident that the road should be as nearly 
straight between the points it connects as the configuration of the 
country traversed will permit. It is desirable, however, to re- 
strict grades to 6 per cent and to avoid expensive cuts, fills 
and bridges. To locate the road properly and meet all local 
conditions in the best manner requires competent engineering 
services; if they are not obtained there is a strong probability 
that after the country develops new locations must be made to 
meet the increased transportation needs and the expenditures 
for new rights-of-way will be far greater than to-day. But if, 
for the present, engineering services are out of the question, the 
road authorities can at least relocate roads that are plainly un- 



2 AMEKICAN HIGHWAY ASSOCIATION 

necessarily low and marshy and unnecessarily steep and high. 
This is particularly the case where roads have been laid out on 
the section lines of the government land surveys. However 
desirable the rectangular parceling of unoccupied land may 
have been in attracting settlers, it has proved a heavy handicap 
on transportation by introducing many right-angle turns and 
causing needless length in the roads of these regions. The fol- 
lowing comment on this condition was made by W. S. Gearhart, 
State engineer of Kansas: 

A 60-foot road on two sides of a section of land occupies 14.55 acres, 
while a road 60 feet wide in a diagonal direction through the section occu- 
pies 10.28 acres. Thus there is a saving in the diagonal road of 4.27 acres 
and 0.587 mile of distance. The saving in the cost of right of way, assum- 
ing that the land along the section line is as valuable as on the diagonal 
line, is $85.40 if the land is worth only $20 per acre. This amount in most 
cases would be sufficient to grade the 1.413 miles of diagonal line in first- 
class condition. If a man lives 4 miles north and 4 miles east of his market- 
place he is 5.657 miles on the diagonal line from it; that is, on the section- 
line road he must travel 4.686 miles farther in making the round trip than 
on the diagonal line. 

The same official has reported that a county commission built 
a mile of road on a section line, which crossed the same stream 
three times. By adopting a somewhat different location and 
making the road IJ miles long, the stream would be crossed but 
once and the road become of greater service to the community. 
^'More than $3,000 worth of steel bridges were bought, it will 
cost not less than about $2,500 for the abutments to set these 
three structures on, and an expenditure of $2,500 will be neces- 
sary to make the road passable, or a total of about $8,000 to 
accommodate four men whose property is reported as probably 
not worth as much as the cost of the road." Instances of this 
nature prove the desirability of having roads located by engi- 
neers without interference from political or personal influences. 
The assertion that such services are unnecessary in connection 
with such relatively inexpensive highways as dirt roads is best 
answered by pointing to the action of the Utah State road com- 
mission in substituting an entirely new location about 15 miles 
long for an old route in Beaver County. This was done by the 
engineers because the new line had better alignment, grades and 
road materials. 

The influence of soil conditions and the presence or absence of 
road materials may not be given due consideration in locations 
made by persons who are not engineers. The following comments 
on this point were made by A. N. Johnson in a report on the high- 
ways of Maryland: 



LOCATION AND GRADES OF RURAL ROADS 3 

Should it happen that two locations are possible with about equal ad- 
vantages and disadvantages, except that one was over a different soil from 
the other, that location should be taken which traverses the soil best cal- 
culated to insure a good road-bed. For example, if it were possible to 
avoid going through a clay section when a more open soil could be had 
close at hand, much would be saved both in the cost of construction and 
in the subsequent maintenance by going over the more open soil. It is 
hardly necessary to state that crossing soft, boggy soil should be avoided 
whenever the expense of going around such a place would be no more than 
for crossing it. If possible it is always well to locate a road in the vicin- 
ity of good road-material, either a suitable stone or gravel, for the prox- 
imity of such material lessens for all time the cost of maintenance of the 
road, and when this point is considered such a location would be war- 
ranted even at an increased first cost. 




Profile op Road in Baltimore County, Md. 

Showing How Relocation Saved a Large Sum in the Improvement of the 

Road. 



Value of Engineering Services. — Few persons realize that the 
expense of engineering services in relocating old roads is gener- 
ally more than offset by the saving in the cost of construction 
of a properly located road over one improperly located. The 
engineer knows how to fit the road to the ground in hilly country 
so that the material from the cuts may be used in making near- 
by embankments and costly rock excavation will be reduced to 
the lowest practicable amount. On the Maryland State high- 
ways, the expense of moving 100 to 150 cubic yards of earth is 
from $50 to $75, which is equal to the cost of making a mile of 
careful surveys that may be reasonably expected to save more 
than 150 cubic yards of such earthwork. The accompanying 
illustration shows the saving in excavation expenses on a road in 
Baltimore County, Md. The hilly character of the old road 
made necessary heavy reductions in grade to give a highway prop- 
erly accommodating the traffic. The heavy cutting to give suit- 



4 AMERICAN HIGHWAY ASSOCIATION 

able grades along the old location is shown by the diagram, 
while the light excavation and filling required on the new loca- 
tion is also indicated. Such savings of cost can only be made by 
competent engineers. The amount of detail which the engineers' 
survey must furnish depends on the character of the road to be 
built and the nature of the country. Less detail is necessary 
for an earth road in a flat country than a brick road in a hilly 
district, for example, but enough should be obtained to make 
sure that the final location is along the line on which the cost of 
transportation plus the interest on the first cost plus the cost of 
maintenance of the road will be the minimum for the available 
funds for first cost. The last point is important, for the best 
location is often governed by the amount of money which can 
be spent on construction. 

In carrying out extensive work by contract, experience shows 
that low bids from responsible contractors are best secured when 
full information is obtained for their use in preparing estimates. 
For instance, in carrying out road improvements in Vermilion 
County, Illinois, under a $1,500,000 bond issue, about 1800 draw- 
ings of plans, profiles and cross-sections were prepared in the 
first two months of the work. These were plotted on Plate 
A 4 by 20 profile paper cut into 32-inch lengths. The longitu- 
dinal scale of the plans was 80 feet to 1 inch and the tranverse 
scale 40 feet to 1 inch. The horizontal scale of the profiles was 
80 feet to 1 inch and the vertical scale 4 feet to 1 inch. The 
plans show all section corners, bench marks, fence lines, shade 
trees, farm entrances, property owners' names, drains and cul- 
verts to be built, and any other data necessary for a complete 
knowledge of the working conditions. The cross-sections are 
plotted on a scale of 4 feet to 1 inch. An 11 by 8i-inch map was 
made of the location of 14 sources of sand and gravel, the plants 
furnishing paving brick and the railways running from them to 
the district where the roads were to be built, and 24 by 20-inch maps 
were made showing the roads, railways and sidings available for 
contractors' use. The existing road grades were shown on small 
maps, and other small maps showed the location and size of pro- 
posed bridges and culverts. 

Grades. — The effect of grades on hauling is usually stated in 
the following manner: If a horse can pull 1,000 pounds on a 
level road, he can pull 810 pounds with the same effort on a 2 
per cent grade, 720 pounds on 2J per cent grades, 640 pounds on 
3^ per cent grades, 540 pounds on 4 per cent grades, 400 pounds 
on 5 per cent grades and only 250 pounds on 10 per cent grades. 
These figures are only approximate but they show the impor- 
tance of reducing grades as much as possible where traffic is heavy. 
Where traffic is not heavy, the cost of reducing grades below 3 



LOCATION AND GRADES OF RURAL ROADS 5 

or 4 per cent, if it must be done by expensive construction or 
considerable lengthening of the road, is generally considered an 
unwarranted expense. 

A thoroughly consolidated roadbed is a valuable public asset 
and in planning grade improvements it is sometimes undesirable 
to cut 6 to 12 inches into such a road for a long distance in order 
to secure a theoretically perfect profile. 

Where a road will probably have considerable automobile 
traffic the grades up a hill should be flattened somewhat at the 
top if necessary, so the driver can see an approaching car when 
it is 300 feet from him. When the change in grade at the sum- 
mit is not more than 6f per cent, no flattening is necessary. If 
the change is 10 per cent a vertical curve about 200 feet long 
should be employed; for a 13 per cent change, a curve 292 feet 
long and for a 16 per cent change, a curve 360 feet long. 

Widths. — Highway commissions in many parts of the country 
are reporting that their roads are often too narrow to accommo- 
date the traffic coming on them as soon as they are improved. 
State Highway Commissioner Everett of New Hampshire re- 
ports that the standard width of 21 feet from ditch to ditch 
is not wide enough on many of the roads under his jurisdiction, 
and the experience of the Wayne County road commission, in 
Michigan, shows that the minimum width of hard-surface road- 
way in the district around Detroit should be 16 feet and 18 feet, 
and should be adopted wherever practicable. These comments 
relate to double-width roads. A width of 8 feet, previously used 
for single-width roadways, is now generally considered too nar- 
row and 9 and 10 feet are advocated. 

Many of the State highway departments have established 
standard cross sections for earth roads. The present standards 
in Wisconsin are shown in the diagrams on the next page. They 
are also the standards for macadam and gravel roads having 
a hard surface 9 feet in width. Where the slopes are not indicated 
they are made in accordance with the accompanying table. 
Guard rails are used when the vertical distance from the edge 
of the shoulder to the top of the ditch is more than 4 feet. 

Slopes Required by Wisconsin Commission in Road Work in Different 

Kinds of Soil 



Sand and sandy gravel 

Loam 

Clay and clay gravels. 

Hard pan 

Solid rock 



2 to 1 
U to 1 
1 to 1 
J to 1 
As it stands 



FILLS LESS THAN 


FOUR FEET 


3 to 1 


3 to 1 


3 to 1 


3 to 1 


3 to 1 



FILLS OVER FOUR 
FEET 

2 to 1 
U to 1 
IHo 1 
1 to 1 
As it stands 



6 



AMERICAN HIGHWAY ASSOCIATION 




© 

'Whenever 1 



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tue 
omoufit of notei- m 
djichss mil begrccri ' 
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HoT Section tor side niTI or dugov/tHoQda 



Standard Earth Road Sections, Wisconsin 



LOCATION AND GRADES OF RURAL ROADS 7 

The Wisconsin sections are wide enough to carry a 16-foot 
roadway. It is now generally held that the distance from ditch 
to ditch should be 24 feet, even for a single-width road, if local 
conditions permit. In some States, where the legal right-of-way 
is only 30 feet, it is impracticable to secure 24 feet between 
ditches and have proper fences and banks along the road where 
it is in cuts. It is necessary to obtain extra wide rights-of-way 
in such cases or to make the road narrow. 

It has been claimed that if a hard surface is placed on a road- 
bed, the width of this pavement need not be so great as when 
the traffic is carried by a less durable surface, and consequently 
a smaller width between ditches and less earthwork are required. 
This argument ignores the fact that a narrow roadway concen- 
trates the travel and may cause the improved surface to carry 
a volume of traffic for which it is unsuited. For this reason 9 
and 10 feet for a single-width surfaced roadway and 16 or 18 feet 
for a double-width roadway are generally favored. In recent 
years a new factor has become important in determining the prop- 
er width of hard surfacing. Heavy motor trucks and omni- 
buses are now in regular service on many roads. If they turn 
off a hard surface on to a soft shoulder they may become mired 
or unmanageable and crash through fences or guard rails before 
the brakes stop them. The driver is usually on the left hand of 
such a truck where he cannot easily see the edge of the hard 
paving, and consequently he keeps his truck well toward the 
center of the road in order to avoid trouble on the shoulders, 
although the driver of a lighter vehicle would keep farther over 
to the side. 

Where the road is used by carts or trucks that make a loaded 
trip in one direction only, as well as in other sections where funds 
are not available at present for a double-width paved roadway, 
an 8 to 10-foot pavement has been laid on half the road, with one 
side along the center line, as though a similar pavement were 
to be laid at once on the other side of the road. 

Rights-of-way. — The width of the road is restricted in the older 
parts of the country by narrow rights-of-way, which are trouble- 
some limitations on road improvements. Cuts and fills of more 
than a few feet widen the strip occupied by the road, ditches and 
side slopes. Telephone poles and trees along the road require 
space, and provision for both is desirable. As a result of long 
experience in Massachusetts and California, reinforced by ob- 
servation in many other States, Austin B. Fletcher, state high- 
way engineer of California, recommmends securing a minimum of 
50 feet for right-of-way, and 60 feet wherever practicable. 

Acquiring rights-of-way is an annoying feature of the work of 
highway commissions, and in any extensive undertaking expe- 



8 AMERICAN HIGHWAY ASSOCIATION 

rience shows that the best results are obtained if the business is 
handled by one man, with whatever assistance is needed. Dip- 
lomatic methods are best but legal warfare is sometimes neces- 
sary, and whatever means must be used should be employed 
promptly in order to have the right-of-way available for construc- 
tion as soon as it is time to begin work. In som.e States, it is un- 
necessary for the authorities to pay for private property taken 
for public use in advance of actually taking possession. If 
the property owner is dissatisfied with the original offer of pay- 
ment or the award made to him by the public authorities, he 
may pursue his remedy in the appropriate court, even though his 
land has already been occupied by the public. In other States 
no rights-of-way can be taken before they have been acquired, 
after a vast amount of red tape, by donation, purchase or condem- 
nation. The western States are particularly oppressed by such 
roundabout methods of entering upon private property to carry 
on improvements for the benefit of the entire community. 

It has been Mr. Fletcher's experience that the expense of ob- 
taining abstracts of title to ascertain the ownership of land is 
unnecessary. The method he has employed in securing rights- 
of-way for hundreds of miles of California highways is the fol- 
lowing: When the field parties are making the original surveys, 
the chiefs of party usually inquire from the occupants of Ihe land 
surveyed who the owners or those interested in the property may 
be. This gives a clue to the ownership. Thereafter one of the 
staff visits the proper county officers and ascertains from the 
assessment rolls or the records who purport to be the owners. 
Deeds or agreements are then prepared, containing the proper 
descriptions, and it is very rare, indeed, that any objection has 
been made to the accuracy of the instrument submitted. By 
thus performing its own title searches, even though thay may 
not have always been the most exact from a title lawyer's stand- 
point, the authorities have saved thousands of doUars and have 
never had an injunction or ejectment proceeding instituted 
against them by objecting land owners. 

Curves. — Sharp curves and right-angle intersections are danger 
places where vehicles move rapidly. The width of the roads 
should be increased on sharp curves, except where it is already 
wide, and the right-of-way at right angle intersections should be 
widened and cleared so as to give drivers on the crossing roads 
a good view of approaching vehicles. This is not always prac- 
ticable, unfortunately, but road commissions should keep in 
mind that these places are dangerous, that it is their duty to 
reduce the dangerous conditions on the roads under their charge 
and that it is less expensive to improve these places now than it 
will be later. 



LOCATION AND GRADES OF RURAL ROADS 9 

On curves on a road with a uniform cross-section there is a 
tendency for the drivers of motor vehicles to stay on the inside 
of the curves because the centrifugal effect of passing on the 
outside is unpleasant. In order to make motor travel equally 
agreeable on any part of the cross-section of curving roads, it is 
now the practice to superelevate the outside of the road, as is 
done on railways. Experiments with different angles of super- 
elevation on California roads have led the highway department 
of that State to adopt a slope of J-inch rise to each foot of width 
of the roadway on all curves having radii of 300 feet or less. 
The transition from the standard crowned cross-sections to the 
uniform transverse slope stated is made in a distance of about 
80 feet. In passing from the straight to the curved road, the 
outside of the road is gradually made horizontal and then grad- 
ually tipped up until there is the same slope throughout the sec- 
tion from the inside to the outside edge. In this transition the 
inside edge remains at the same elevation it would have if the 
ordinary crowned cross-section were maintained; the change 
is made by adding to the height of the other parts of the standard 
section, so the improvement is generally called ''banking the 
curves.'' 

Grade Crossings. — The elimination of grade crossings is a prob- 
lem that frequently complicates the location or relocation of 
highways. The usual method of carrying the road under or over 
the railroad tracks is so costly that its general use on rural roads 
is impracticable. Some of the narrow underpasses with sharply 
curving approaches that have been built on roads used by numer- 
ous automobiles at high speed are almost as dangerous as the 
grade crossings they replace. Attention is therefore being given 
more and more to comprehensive relocation as a means of re- 
ducing the number of grade crossings and making those remain- 
ing less dangerous than before. For example, there was a Wis- 
consin road 23.9 miles long with 16 grade crossings and 15 
such crossings on branch roads feeding it, in addition to 3 under- 
passes and 2 overhead bridges. A careful study by the State 
highway commission showed that by reasonable relocation the 
total number of crossings could be reduced to 16 at grade, 4 
underpasses and 2 overhead bridges, and the 16 grade crossings 
would be on the branch roads, none remaining on the main road. 
The total cost of right-of-way and construction for such an im- 
provement was estim.ated at $35,000, much less than the cost of 
elimination in the usual manner. 

The New York State highway department has had a long 
experience in treating grade-crossing problems and as a result 
has adopted the following general rules for location at such 
crossings: 



10 AMERICAN HIGHWAY ASSOCIATION 

1. The alignment should be laid out so that approaches are 
on a tangent which is at least 400 feet long, 200 feet on each side 
of the crossing. The angle that the highway makes with the 
railroad should not be less than 60 degrees. The grade of the 
approaches should not be greater than 6 per cent, and there 
should be a portion level or nearly so for a distance of not less 
than 100 feet on each side of the crossing. 

2. On the highway within 200 feet of the railroad, on each 
side, traffic should have a clear view of approaching trains for a 
distance of 1,000 feet. (See Rule 5.) 

3. The width of the planked crossing shall not be less than 
24 feet, measured at right angles to the center line of the high- 
way. The ends of the pavement should be protected by an edg- 
ing of stone or concrete placed at a sufficient distance from the 
ends of the ties to allow for replacing them. 

4. A standard danger sign should be placed at each side of 
the crossing along the highway in a prominent location at least 
400 feet from the crossing. 

5. When the view of the railroad either way, as required in 
2, is less than 1,000 feet, or when there is a great deal of traffic 
on either the highway or railroad, or when vision may be 
blocked by cars or trains as in the case of a railroad with two 
or more tracks, a flagman should be employed to warn highway 
traffic. 

The New York State highway department's rules for the elim- 
ination of grade crossings are as follows: 

1. Subways shall have a clear head-room of not less than 13 
feet and a clear width between abutments of not less than 26 feet. 
The approaches when in a cut shall have a minimum width of 
28 feet between bottoms of slope. When a highway passes over a 
railroad the clear height over said railroad shall be not less than 
21 feet and the approaches when on embankment shall be not 
less than 28 feet wide across the shoulders. 

2. The alignment and grade of approaches shall be such 
that traffic at any point within the limits of the elimination 
will be able to see that approaching it for a distance of 300 feet. 
The maximum allowable grade shall be 6 per cent. 

3. Bridges carrying railroads over highways shall be of a 
solid-floor, ballasted type. Drainage of such floors shall be 
such that water will not drop upon the roadway. Bridges car- 
rying highways over railroads shall have solid concrete floors 
with a minimum width of roadway of 18 feet. 

4. When an elimination is made on a highway already im- 
proved, the pavement shall be of the same type as the existing 
pavement. If the highway is not improved the pavement shall 
be the same as that contemplated. 



LOCATION AND GRADES OF RURAL ROADS 11 

5. Subways shall be drained in a thoroughly satisfactory 
manner. 

6. The limits of an elimination shall be taken as the points of 
intersection of the approach grades of the elimination with the 
grade of the existing highway. 



REGULATIONS OF THE CALIFORNIA HIGH- 
WAY COMMISSION REGARDING 
SURVEYS AND PLANS' 

Part 1, Surveys 

(a) Note Books. — Survey note books will be furnished to the 
chief of party by the Division engineer. No survey note book 
other than the standard book so furnished shall be used, and 
the use of loose sheets is prohibited. The notes placed therein 
shall be the ''original" notes of the survey and shall not be copied 
from sheets or from other books. 

The standard book shall be used for alignment, topography 
and levels, and for all other information which the survey parties 
are required to secure; all notes shall begin at the bottom of the 
page and read upward. 

On beginning a survey the chief of party shall see that a proper 
entry of the Division, coimty and route, is made upon the label 
pasted to the inside of the front cover of the note book. 

Attached to the back cover of each book are several pages 
showing the ''standards" required in all surveys. All survey 
notes shall conform in so far as possible to such "standards" to 
the end that all surveys and the manner of taking the notes thereof 
shall be uniform throughout the work. 

At the beginning of each day's work the following data shall 
be entered in the book: Date; weather conditions; names of 
members of party and duties of each. 

When no notes are taken on a working day or portion of a 
day, the date shall be entered and the reason for the loss of time 
shall be stated clearly and concisely. 

All survey and other notes shall be suitably indexed on the first 
ruled page of the note book. 

Every day at the close of the work the notes shall be copied 
neatly upon specially printed sheets furnished by the division 
engineer and numbered consecutively, and after careful check- 
ing such sheets shall be forthwith forwarded to the division 
engineer. 

No note book shall contain notes relating to more than one 
route or to more than one county. 

1 From Austin B. Fletcher, State Highway Engineer of California. 

12 



REGULATIONS OF THE CALIFORNIA HIGHWAY COMmsSION 13 

(b) Alignment Notes. — The base line of the survey shall be 
referred to the true meridian, which shall be determined by ob- 
servation on polaris. The chief of party before beginning a sur- 
vey shall procure all tables and other data needed for such deter- 
mination and observations shall be made from time to time to 
ensure the accm'acy of the work. The line shall also be checked 
by magnetic bearings taken at each transit point. All angles 
in the base Hne shall be azimuth angles read from the back sight 
and repeated with the telescope reversed. 

Complete traverses shall be run in all surveys and computed 
in the field. If the error of closure exceeds 1 : 5000 the division 
engineer shall be notified and the party shall not move camp imtil 
he has authorized such moving. The closures shall be completed 
and computed in such lengths as the division engineer shall 
prescribe. 

The base line shall be as nearly as may be in the center of the 
proposed road. When it is apparent that a tangent base line will 
not follow the approximate center of the proposed road, a curve 
of suitable radius shall be run. Curves shall be measured by 
computing the length of the arc and not by chords. 

If the survey follows an existing road, wire nails not less than 
5J inches in length shall be driven flush with the traveled way at 
all angle points in the base line, at the beginning and ending of 
all curves and on long tangents at intervals not exceeding 1000 
feet. 

When the base fine does not follow a traveled way or when the 
roadway is so soft that nails will not hold their position, wooden 
stakes driven flush with the ground shall be used and the transit 
point indicated thereon by a small nail. 

All transit points shall be properly referenced as provided 
under the caption ''Stakes." 

Stations shall be estabhshed every 100 feet on the base line 
and indicated by short wire nails driven through bits of red 
cloth into the ground to serve as temporary markers during the 
survey. The stations and half stations shall be also permanently 
marked by stakes set on both sides of the proposed road suffi- 
ciently far removed from the base line to prevent their being dis- 
turbed during the building of the road. 

(c) Stakes. — All stakes which are to be used for estabhshing 
grades shall be made from 2x3 inch scantling, from 24 to 30 
inches in length, laid flat and sawed diagonally into two wedges, 
with the sharp ends approximately J inch thick. The lumber 
from which the stakes are made shall be sound, reasonably free 
from knots, and planed on all sides. These stakes shall be driven 
into the ground to about one-half of their length with the 2-inch 
face parallel to the base hne. On the right side of the road the 



14 AMERICAN HIGHWAY ASSOCIATION 

station number shall be marked plainly on the side of the stake 
facing Station O, and on the opposite side of this stake shall be 
marked to the nearest tenth, the offset from the base line. The 
face toward the road must be reserved for marking during con- 
struction. On the left hand side of the road, the offset from the 
base line shall be marked on the side of the stake facing Station 
O and the station number on the opposite side. 

All stakes used to mark monuments and for transit points shall 
be wedge shaped, not less than 1 foot in length nor less than | x 
2-inch at the top. Such stakes shall be driven flush with the 
groimd unless they are so located as not to endanger the travel- 
ing public. Short nails driven into the tops of these stakes shall 
indicate the monument and transit points. 

All monument and transit points shall be referenced by three 
ties to natural objects or, if such do not exist, to stakes, as shown 
by the ''standards" at the back of the note book. 

(d) Topography. — All objects, such as houses, barns, fences, 
gates, field entrances, trees, telephone and telegraph poles, power 
lines, railroad and railway tracks, within a distance of 150 feet 
on either side of the base line shall be located by offsets from the 
base Une and recorded in considerable detail, and the limits of 
the ''traveled way" on all existing roads shall be indicated. 
Separate sketches, with levels and dimensions of all essential 
features, shall be made in the note book of all bridges, large cul- 
verts and other appurtenances of the road, and plainly refer- 
enced in the topography notes. 

The azimuth from the back sight to the boundary lines of all 
incorporated cities and of all counties shall be ascertained and 
recorded. The azimuth of the boundary lines of all entering 
and intersecting highways, of township lines, and of division 
lines between property holdings shall be ascertained and re- 
corded with reasonable accuracy, and when feasible the names 
of the owners of property abutting on the proposed road shall 
be recorded. 

When it is desirable to locate topographic features from a 
sub-tangent, the station will be measured from the nearest end of 
the curve. 

(e) Levels — Whenever there is a known government bench 
within 3 miles of the survey, the datum plane of such bench shall 
be adopted for the work. If no such bench is available, a datum 
plane shall be assumed at such an elevation as will be low for all 
parts of the survey. 

Benches shall be established during the progress of the work 
at each end of the survey, at city and county lines, and at other 
convenient points not more than 1000 feet apart, and at shorter 
intervals on grades. 



REGULATIONS OF THE CALIFORNIA HIGHWAY COMMISSION 15 

Where no permanent objects or structures exist, a long, sub- 
stantial stake shall be driven firmly into the ground and prop- 
erly referenced. 

On bench marks, at turning points, and on construction stakes, 
elevations shall be determined to hundredths of a foot. 

Cross section levels shall be taken to tenths of a foot at each 
100-foot station and at half stations, at entering and intersecting 
roads, for not less than 200 feet from the base line, at driveways 
and field entrances and wherever the surface of the ground changes 
abruptly. The elevation of the center of the traveled way of 
an existing road shall be taken and properly noted when it does 
not coincide with the base line. The cross sections shall include 
the whole width between fences, and where the grade is likely to 
be changed substantially the cross sections shall cover a width 
sufficient to include all groimd likely to be affected. 

Sections shall be taken at all culverts and water crossings, and 
elevations shall be taken a sufficient distance up and down all 
streams to afford data for designing new structures. 

(f) General Data. — The survey notes shall contain data con- 
cerning: 

1. The location of outcropping boulders and bedrock, suitable 
for road metal or concrete. 

2. The location of all quarries near the proposed road. 

3. The location and approximate quantity of field stone 
available in the vicinity of the road. 

4. The location of all gravel pits. 

5. The location of points where good river sand can be obtained. 

6. The available points where water for sprinklers and steam 
rollers can be obtained. 

7. The location of all railroad spur tracks or sidings within rea- 
sonable haul of the proposed highway and the name of the railroad. 

8. The most advantageous locations for rock crushing plants 
along the road. 

9. The current wages paid to teamsters and laborers in the 
locations through which the road will pass. Amount paid for 
hire of mules or horses (without driver) per day. Amount paid 
for man and two-horse team per day. 

10. The locations where special underdrains should be in- 
stalled due to the existence of unstable sub-soil conditions. In- 
quiry should be made of residents and local officers regarding 
spots that break up badly in wet weather. 

11. The approximate area of the watershed at each stream 
crossing if it can be readily obtained. All high-water marks 
should be noted and inquiry as to whether or not water over- 
flows the road. 

12. All general information that may prove of value in the con- 
struction of the highway. 



16 AMERICAN HIGHWAY ASSOCIATION 

Part II. Plans 

(a) Drafting. — All drafting so far as possible shall be done in 
the division offices. At the Sacramento headquarters, the draft- 
ing shall be limited to work of a general nature, such as the de- 
sign of standards, general maps and to such revision work of 
the plans made in the division offices as may be necessary. No 
drafting shall be done in the survey party camps except such as 
's immediately needed in the mountainous country to facilitate 
u:^ choice of lines and grades. 

'i: -^ plans, profiles and cross-sections shall be plotted in the 
divisio.i offices from the copies of the survey notes sent in daily 
by the sui '^ey parties as required under the rules for surveys. 

(b) Worh.. '^n Plans. — The plan and profile of every road survey 
shall be plottt. ^ on detail paper 30 inches in width and of such 
length as may be found convenient, the plan to be plotted above 
the profile, and such drawings shall be known as the '^Working 
Plans." 

Plans and profiles shall be plotted from left to right, the plan 
on the scale of 1 inch to 100 feet and the profile to the same hori- 
zontal scale and to the vertical scale of 1 inch to 20 feet. 

The base line of the survey shall be plotted by coordinates 
obtained from the traverse sheets which have been made and 
calculated in the survey camps and said base line shall be inked 
in red before the topography is plotted. All angles and curve 
points shall be marked by small circles, and the even stations by 
a line | inch in length drawn at right angles across the base line. 

The even stations and the plus distance of all angle and curve 
points shall be numbered below the base line. The calculated 
bearings of the base line, together with the tangent and curve 
lengths and the radii of the curves, shall be indicated above the 
fine. The right-of-way lines shall be shown in red. They shall 
be properly referenced to the base line and land corners. Where 
they are not parallel to the base line their bearings and lengths 
shall be indicated. The topography and lettering other than 
that relating to the base line shall be done neatly and so as to 
permit of tracing easily but such details shall not be inked. 

All drafting details shall conform to the conventions shown on 
the specimen sheet furnished to each drafting office. 

The north point shall be indicated at intervals of not more 
than fifty stations. 

The datum line of the profile shall be drawn f inch from the 
bottom of the sheet and inked in black. Perpendiculars shall be 
erected at each even station and inked in black. The even sta- 
tions and plus distances shall be numbered below the datum line 
and the elevations of the present sm^face of the ground shall be 



REGULATIONS OF THE CALIFORNIA HIGHWAY COMMISSION 17 

shown above the datum line and to the left of the perpendiculars. 
The elevations of the proposed finished road surface shall be 
shown in red and to the right of the perpendiculars. 

The present ground surface shall be drawn in black, and the 
proposed finished surface of the road and proposed rates per 
cent of grade in red. Points of change in the rate of the finished 
grade and the beginning and end of vertical curves shall be in- 
dicated by small circles. 

No title need be placed on the working plans; they shall be 
identified b}^ the file number, and such plans shall bear the sig- 
natures of the employees concerned in their preparation and the 
date. 

(c) Cross Sections. — The cross sections shall be plotted to the 
scale of 1 inch to 5 feet vertical and horizontal on specially ruled 
sheets, 20 by 30 inches in size, furnished by the highway engi- 
neer. They shall be plotted from the bottom of the sheet up- 
ward and so as not to interfere with one another more than is 
necessary. The station numbers shall be placed directly below 
the datum line and across the base fine. The present ground 
surface, the elevation at the base line and the station number 
shall be inked in black. The proposed finished surface, together 
with the elevation at the center of the proposed roadway, shall 
be shown in red. 

(d) Layout Plans. — The layout plans shall be on tracing cloth 
20 by 30 inches in size and the first sheet shall carry the title, 
small index or key maps, conventions, and the necessary certifi- 
cates and signatures, and such sheet will be prepared in Sacra- 
mento. The subsequent sheets shall be traced from the working 
plan, shall be authenticated by the signatures of the division 
engineer and the highway engineer, shall state the whole num- 
ber of sheets in the set and the number of the individual sheet, 
the file number, and on each sheet shall be shown the true North 
Point. These plans shall conform as closely as is practicable in 
workmanship and appearance to the specimen sheet hereinbefore 
referred to. 

(e) The Grade Line. — The grade shall be established tenta- 
tively on the profile under the direction of the division engineer 
and transferred to the cross-sections and the proposed finished 
surface of the roadway and slopes shall be drawn on the sections 
with the aid of templets to be furnished by the highway engineer. 
If it appears to be desirable to shift the center of the roadway 
from the base line, the new alignment shall be located on the 
working plan by a dotted redline. The limits of earth work 
shall be shown on the plan by a dotted red line where they ex- 
tend beyond the fences or known right-of-way lines. 

After the grade line has been so tentatively established and 



18 AMERICAN HIGHWAY ASSOCIATION 

the estimates have been completed, the working plan, cross-sec- 
tions and estimates, together with sketches of special structures, 
shall be submitted to the highway engineer for his scrutiny. 

(f) Accessions. — Every plan made in a division office and which 
is to remain there after it has been signed by the division engi- 
neer, shall be entered in the ''Accession Book'' and described as 
required by the captions therein. All other plans and maps re- 
ceived at such offices, and which are to remain there, shall be 
likewise entered in said book. 

(g) Filing of Plans and Note Books. — All plans shall be filed 
flat in drawers in the division offices but during their prepara- 
tion the working plans may be rolled and folded afterward. 

When completed, the layout plans shall be filed at Sacramento 
headquarters and on the completion of a contract the cross- 
sections shall be Hkewise filed at Sacramento, blue prints thereof 
being furnished to the division offices. 

AU note books shall be filed at Sacramento when the contract 
relating to the surveys therein is completed. 

All documents, whether plans, books or papers, which relate 
to road contracts shall be stamped with the file mark adopted. 



DRAINAGE, CULVERTS AND BRIDGES^ 

In most parts of the country water is one of the most destructive 
influences on roads. When it collects on the surface it tends to 
injure the roadway unless the latter is paved with some hard, im- 
pervious material. The mudholes on earth, gravel and broken 
stone roads become soft, so that traffic increases their area and 
depth rapidly. The impervious crust is finally broken through, 
allowing water to reach the roadbed, which gives way under heavy 
loads and the condition of the roadway becomes very bad. If 
water collects in the ditches, it percolates sideways into the road- 
bed, softening it and eventually causing subsidence which produces 
marked irregularities in the surface, so that mudholes form there. 
If the subgrade on which the roadbed is carried is soggy, a road 
can not be maintained on it. Charles J. Bennett, State highway 
commissioner of Connecticut, has reported an instance of this in a 
city where a 7-inch broken stone roadway was placed on a poorly 
drained clay subgrade. The roadway broke up when frost came 
out of the ground and became so impassable that stringers were 
laid on it and covered with crossplank to furnish a driveway. 
This heaving action of frost will eventually destroy any roadbed 
in which water is allowed to collect. The water expands every 
time it freezes. The expansion opens up the earth, so that gradu- 
ally more water enters it and finally there is so much in the pores 
and cracks that its expansion throws up the roadway. 

Troubles with water are particularly noticeable on grades. The 
water is not shed so quickly from the roadway on steep slopes as 
it is on fairly level roads, but runs toward the side ditches at an 
acute angle with them. If there is any check to the flow at the 
side of the roadway, such as irregularities of the surface or vege- 
tation offer, some scouring will eventually take place, and it is for 
this reason that the good condition of the shoulders of steep roads 
is important. The scouring of ditches on steep grades is a com- 
mon occurrence after heavy rains, and experienced maintenance 
men regard it as an injury that must be repaired immediately. 
If the road is on a fill and also on a grade, the handling of water 
requires special care if heavy gullying of the slopes is to be 
avoided. A gully may be cut a quarter of the way across a new 

^ Revised by W. F. Childs, Jr., Resident Engineer, Maryland State Roads 
Commission. 

19 



20 AMERICAN HIGHWAY ASSOCIATION 

road in such a location by a single heavy rain. An unusual case 
of the effect of water on slopes has been mentioned by Mr. Ben- 
nett. A road which led up a steep hill was originally only wide 
enough for one vehicle and was the drainage channel for the sur- 
face water of the hillside. The surfacing was washed away by 
every heavy rain. A new road was built by filling in stone to a 
depth of 4 feet, with an open box culvert at the bottom to carry 
whatever water might penetrate beneath the road from the sides. 
This stone fill extended the entire width of the road, from shoulder 
to shoulder, and very deep, wide ditches were provided at each 
side. There has been no trouble with this road since it was re- 
constructed in this way, showing what good drainage can do even 
in an exceptionally bad place. 

In any drainage work it is necessary to allow for the different 
water-holding capacities of different materials. Experiments by 
the United States Office of Public Roads and Rural Engineering 
show that with the same condition of dryness, clay will take up 
more water than sand, but will not part with so much. The rate 
of drainage from saturated sand is almost twice as fast as from 
saturated clay during the first twenty-four hours after the mate- 
rials are allowed to drain. Silt is the slowest material to drain 
and the loams come between sand and clay. While silt and clay 
absorb more water than sand, they allow water to percolate very 
slowly indeed in comparison with sand, and it is for this reason 
that they form water-tight barriers when confined so their grains 
can not flow away. When in a loose condition silt permits the 
smallest amount of percolation, and calling the rate with this 
material 1 the rate with loose clay is nearly 3, loose sandy loam 
nearly 28 and loose sand nearly 54. With compacted materials, 
however, such as exist in a well-built roadbed, the lowest rate of 
percolation is with clay; calling it 1, the rate with compact silt is 
2, compact sandy loam 15, and compact sand 93. The experi- 
mental investigations make clear the reason for particularly care- 
ful drainage of clay and silt subgrades. 

General Methods of Drainage 

Road drainage is chiefly a matter of, first, climate; second, 
topography; and third, soil. It may be treated separately under 
two heads, surface draining and sub-surface or under-drainage. 

In the case of surface drainage, the surface water may be shed 
in four ways, first, by cross-slope or crown in construction; sec- 
ond, by longitudinal grade after the crown is determined; third, 
by discharge into natural water-courses; and fourth, by discharge 
into artificial outlets. 

The crown should be determined by, first, character or type of 



DRAINAGE, CULVERTS AND BRroOES 21 

road; second, the locality; and third, by grade. The crown for a 
natural earth road or a shell road should be made from 1 to 2 
inches higher in construction than that which is ultimately de- 
sired. This opinion is based on the fact that these types of roads 
are more susceptible to consolidation and displacement under 
traffic than most other roads. 

In thickly populated districts a high crown is dangerous to 
traffic and the cross-slope of roads constructed through towns or 
other thickly populated districts should be reduced to that which 
is just sufficient to shed water to the gutter line. In such dis- 
tricts high crowns cause a sliding motion of vehicles and bring 
an extra strain upon lower portion of the wheels which is objec- 
tionable and causes public criticism, which, if not considered, 
brings about a certain amount of prejudice against modern road 
construction. Finally, in considering crowning of roads the ques- 
tion of grades must not be overlooked. Ordinarily the practice 
is to increase the crown as the grades become steeper. For all 
grades up to and including 5 per cent, the crowns mentioned in 
the next paragraph are considered sufficient. "When the grade is 
in excess of 5 per cent the crown should be so increased that the 
water will be shed to the side of road rather than run down its 
surface or, at least, make a curve in its course of final dis- 
charge. 

The minimum and maximum crowns which it is desirable to 
use may be determined by multiplying half the width in feet of 
the hard-surfaced roadway by J to 1 inch for gravel roads, J to 
f inch for macadam, J to J inch for roads with a bituminous sur- 
face, and I to f inch for brick and concrete. Formerly curved 
cross-sections were used with impervious pavements, which were 
quite flat at the center and increased in curvature toward the 
sides, with the result that there was a wholly needless slope at the 
latter. This has been changed of late, and there is a tendency to 
use uniform slopes from the sides toward the center, where an 
angle is avoided by introducing a very flat curve. The unpaved 
shoulders are often given a slope of 1 inch per foot of width. 

There are two general methods of draining the roadbed, by side 
ditches and by underdrains, which will be explained in more detail 
later. In flat country, the roadbed is best kept dry by raising it 
above the neighboring land, just as railway roadbeds are raised. 
If this is not done, it is very difficult to keep roads in good condi- 
tion. 

In undeveloped swamp country, George W. Coolej^, State en- 
gineer of Minnesota, has found the most permanent roadbeds can 
be built by constructing the embankment of material dredged from 
a drainage ditch on the upper side of the road and a smaller ditch 
on the lower side. When the swamps have soundings of 2 to 5 



22 AMERICAN HIGHWAY ASSOCIATION 

feet, he considers that the elevation of the bottom of the dredged 
ditch may be disregarded except that it should not be above the 
suitable theoretical grade line. This is because the surrounding 
land is swampy at all times and the subgrade can not be drained 
by any means short of draining the whole swamp. 

In ordinary flat prairie country, the elevations recommended by 
H. E. Bilger, road engineer of the Illinois highway department, 
vary with the kind of soil used in the roadbed, as follows: with 
dense clay or gumbo, where the obtainable grade of the side ditch 
is less than 0.4 per cent, not more than 800 feet of earth road in 
one stretch should have its crown less than 12 inches above the 
adjacent fields, unless the road is along a ridge or on a side hill so 
that culverts will dehver the water from the uphill ditch to nat- 
ural outlets on the downhill side. In partly impervious soils, 
such as loams, the same elevation should be maintained, when 
the side ditches have a slope of less than 0.2 per cent. With sand, 
gravel or very loose soil, the crown should be 6 inches above the 
adjacent fields. 

It is troublesome enough to care for the surface and under- 
ground water on the right-of-way, without having the work ag- 
gravated by water from adjacent property. On hillsides, there- 
fore, the water flowing down the slopes toward the road is often 
intercepted by ditches along the crest of the cuts, as shown in 
Cross-Section 2 on page 6, and carried away to suitable outlets. 
Such ditches are sometimes called ''berm ditches." In sections 
where irrigation is practiced, considerable trouble is sometimes 
experienced as a result of the overflowing of the road, and to pre- 
vent this the following law has been enacted in Colorado: 

No person or persons or any corporation shall cause waste water, or the 
water from any ditch, road drain or flume, or other place, to flow in or upon 
any road or highway so as to damage the same, and any such person, or 
persons or corporation so offending or violating any of the provisions of 
this section for which there is no specific penalty provided shall pay a fine 
of not less than $10 nor more than $300 for each offense, and a like fine of 
$10 for each day that such obstruction shall be suffered to remain in said 
highway, and shall also be liable to any person, or persons or corporations 
in a civil action for any damages resulting therefrom; and it shall be the 
duty of the road overseer in the district in which such violation shall occur 
to prosecute any person, persons or corporation or corporations violating 
the provisions of this act. 

The water accumulating in the ditches should be discharged as 
quickly as possible into neighboring outlets. After light rainfalls, 
this may not seem important, but when a heavy rain occurs in the 
early spring while the roadway is impervious the need of numer- 
ous outlets is evident. This is particularly true on slopes, where 
a large quantity of water in the ditches is liable to scour them 



DRAINAGE, CULVERTS AND BRIDGES 23 

badly. As it is not always practicable to find natural drainage 
channels on each side of the road, culverts must be built to carry 
the water under the roadway from one ditch to the other, as well 
as to provide adequate channels for the brooks crossing the rights- 
of-way. 

Although properly designed and well-built culverts protect a 
road-bed from injury, it is sometimes desirable to avoid the use 
of large structures of this class if it can be done by relocating the 
road. This is particularly the case where the beds of the streams 
are in alluvial soil which is readily eroded by swiftly moving flood 
waters. In such cases there is uncertainty whether unpaved 
channels to and from the culvert will not become so eroded that 
the structure will settle. Culverts of large size in such locahties 
are comparatively expensive, and if there are many of them, it is 
always well to ascertain if the number can not be reduced by chang- 
ing the position of the road. In a few cases winding brooks have 
had straight channels dug to accomplish the same purpose. This 
is particularly the case in districts where the roads follow straight 
section lines without regard to topography. 

The most elaborate investigation of surface and underground 
roadbed drainage that has been made in this country was under- 
taken by a committee of the American Railway Engineering Asso- 
ciation, which reached the following conclusions: 

Side ditches should be provided in cuts, whether the subgrade 
be in rock or earth. The minimum side ditch should be 1 foot 
wide on the bottom and 1 foot deep below subgrade. The mini- 
mum grade for side ditches should be 0.30 per cent If the rate 
of grade of the track in any cut is less than 0.30 per cent, the cut 
may be widened to permit side ditches to be constructed on 0.30 
per cent grades, or drain pipes m.ay be laid to proper grades below 
the ditches to any available outlet. 

Efficient subdrainage of wet cuts and of saturated soil upon 
which embankm.ents rest may be attained by the use of pipe 
drains. They should be laid immediately below the center of the 
side ditch in cuts and about 10 feet from the toe of the slopes of 
embankments and on grades of not less than 0.20 per cent. Care 
should be taken to locate the pipe at such depths that no dis- 
placement will be made in its alignment by the subsidence of the 
roadway under traffic. To this end the trench in which the tile 
is to be laid should be dug down into a motionless stratum under- 
lying the saturated material which it is desired to drain. The 
trench above the pipe should be completely filled with cinders or 
other porous material which filters the water and aids its passage 
to the pipe and prevents the intrusion of the saturated material 
under pressure of traffic. 

A water pocket beneath the track m.ay be drained by small 



24 AMERICAN HIGHWAY ASSOCIATION 

cross drains laid in cinder-filled trenches, or by trenches filled 
with cinders, gravel or similar material. 

The committee recommended that no pipe be used with an in- 
side diameter of less than 6 inches, except for cross drains. It 
will rarely be necessary to use larger sizes than 12 inches. The 
trench should not be wider than is needed for digging it economi- 
cally and laying the pipe. 

Surface intercepting ditches should be constructed on the up- 
hill side of all cuts where they may be opened without causing 
slides. Open ditches should be dug along, and about 10 feet from, 
the toes of embankments resting on soil liable to become unstable 
if saturated, to divert water flowing toward the embankment. 
Where an open ditch may endanger such an embankment, a drain 
pipe may be laid along the toe of its slope. In constructing ditches 
on slopes above cuts, they should not be larger than necessary in 
order that they may not become the notch or score from which a 
slide will start. They should be 10 to 25 feet from the crest of 
the cut, and the material excavated from them should be deposited 
on the side nearer the roadbed. 

Side Ditches 

The cross-section of side ditches should be such that they can 
be formed and maintained by road machines, if practicable, for the 
use of such equipment in places for which it is suitable gives the 
desired results at lowest cost. The sections shown on page 226 
illustrate the capabilities of road machines. In the final shaping 
of the road, care must be taken not to dig the ditches too deep at 
any place, leaving a depression to hold water. The purpose of a 
ditch is to carry water away without retaining any of it. If any 
depressions exist they must be remedied in some effective manner. 

Very good results can be had by making side ditch 2 feet wide 
on the bottom with a 4 : 1 slope on the road side and a slope on 
the back side equal to the angle of repose of the particular mate- 
rial encountered in the excavation. The 4:1 slope on the road 
side is not dangerous to traffic, the slopes can be grassed with a 
good texture of grass and the slope is not so steep as to become 
gullied by water shed into the ditch from the surface of the road 
where the crown is excessive or the grade steep. The slopes can 
also be made and maintained with a road machine. 

The grade of the flow-line of the ditch should be 0.5 per cent if 
possible, rather more than the recommendation for railway ditches 
previously quoted, but in flat country it is sometimes impracticable 
to secure such a grade. Under such conditions the grade lines for 
the ditches should be given by a surveyor, and the excavation 
made to conform exactly to the lines. When finished, these flat 



DRAINAGE, CULVERTS AND BRIDGES 25 

ditches must be maintained on the true grades, or water will fail 
to run off quickly. Flat ditches are often made wide and shallow, 
60 as to expose as much water to evaporaton as possible, and on 
well-maintained level roads care is taken that these shallow ditches 
are not unduly shaded by trees and shrubs, so that evaporation 
will be checked. 

Where there are two convenient outlets with a side ditch run- 
ning from one to the other, the grade may be improved and a 
deep, unsightly ditch avoided by selectmg a good intermediate 
summit and drawing water both ways to the outlet. This summit 
may be regulated by the grades desired or by holding them from 
6 to 12 inches below the sub-grade at the summit and running 
straight flow-line grades each way to the outlets. 

Deep, narrow ditches with steep sides have two defects fre- 
quently observed where roads are not maintained properly. One 
defect is the danger they offer to vehicles which may be crowded 
into them for any reason. The records of the Iowa State high- 
way commission for September, October and November, 1916, 
show that in that State alone 353 automobiles turned turtle, re- 
sulting in 5 deaths and 451 injuries. Just how many of these ac- 
cidents were due to ditching the cars is not stated, but this is gen- 
erally regarded as the usual cause of overturning. Where the 
ditches are deep or the road is on an embankment with steep 
slopes, substantial guard rails should be provided. During Sep- 
tember, October and November, 1916, the Iowa records show that 
167 cars went over embankments, killing 7 persons and injuring 
234. Such a list points more clearly than general arguments to 
the great importance of guard rails that will act as real guards. 

The second defect is the relatively high velocity which water 
may acquire in a deep, narrow ditch. If the latter is protected 
against erosion high velocity may cause no trouble, but such pro- 
tection is not common and when the water rushes through an 
earth ditch the latter will become eroded and both the roadbed 
and the bank may be severely injured. 

The maintenance of ditches cut in earth on slopes is hardly 
possible unless water-brakes are constructed in them. These 
are usually heavy timbers placed across the ditch and projecting 
several inches above it. They check the flow of the water at 
intervals down the hill, and thus prevent a velocity which will 
be destructive. The ditches where they are used must be cleaned 
out after every rain or the bottoms will become filled to the top 
of the timbers and later storms will gully the road and the banks 
at their ends. In some cases, the water-brakes are heavy con- 
crete beams. Where the water attains an erosive velocity in 
ditches paving protects them better than the waterbrakes. 

Wherever practicable ditches in earth on grades exceeding 



26 AMERICAN HIGHWAY ASSOCIATION 

5 per cent should be paved. This adds somewhat to the first 
cost, even when field stone suitable for the purpose can be ob- 
tained in the vicinity, but the first cost is offset by the reduced 
expense for maintenance. 

The outlets from the ditches should receive careful attention, 
because they are frequently a source of needless expense for 
maintenance. There should be a paved channel of sufficient size 
leading from the ditch to the waterway into which the water 
is discharged. If field stone for such a pavement can not be 
obtained, it will be advisable to employ concrete. 

The protection of the embankments by grass or other vege- 
tation is a remedy for scouring used on many railways and 
some highways. Witch grass is a good species for the purpose, but 
must not be used near cultivated land. Bermuda grass and red 
top have been recommended for some localities and other varie- 
ties are probably better suited for different local conditions. 
On the Southern Railway the banks have been held by planting 
the volunteer or Japanese honeysuckle in parallel horizontal 
rows about 10 feet up the slopes. Where the slopes stand satis- 
factorily except during heavy rains, and the material is such that 
vegetation will not grow on them, they are sometimes held in 
place by covering them with coarse cinders and gravel. This 
prevents the water from coursing down them unchecked and 
thus checks erosion. 

At every driveway from a road into adjoining property, there 
is likely to be an obstruction of the ditch crossed by this drive. 
If the ditch is shallow with gently sloping sides, the best drive 
from a drainage viewpoint is a paved strip from the roadway 
across the ditch into the property. Unfortunately this is not 
often practicable and rarely adopted when it is. The usual 
driveway is formed by filling dirt over a flimsy plank drain or 
a line of 4-inch tile on an insecure foundation, and this affords 
wholly inadequate drainage. A culvert with an ample water- 
way should be provided, with a substantial facing or headwall 
at each end. Sometimes culverts under driveways can be omitted 
in the case of shallow side ditches, by locating a summit at the 
entrance and running the grade down in both directions from it to 
well-defined outlets. 

At such drives attention should be paid to the amount of 
water they may discharge into the side ditches. Sometimes on 
a hillside a driveway will discharge a large volume of water at 
such a high velocity that, unless properly led away, part of it 
will flow across the road to the other side, which does the 
shoulders and roadway no good and may cause serious injury. 



DRAINAGE, CULVERTS AND BRIDGES 27 

Underdrainage 

The usual method of repairing a wet place adopted by an 
untrained roadbuilder is to dump stone over it. After the stone 
has been forced into the mud by the traffic, more stone is dumped 
there, with the result that a mudhole is formed at each end of 
the stone fill. The water is in the earth and must find an outlet 
somewhere. Instead of trying to seal it up, the proper remedy 
is to carry it off by some kind of underdrainage. The problem 
of caring for underground water is, first, a matter of soils; second, 
a matter of topography; and third, one of temperature. There 
are many soils of a gravelly, sandy, or similar character, which 
ordinarily are self-draining to a degree and do not require par- 
ticular attention. The difficulty is with those highways built on 
clayey or loamy soils which are more or less retentive and do not 
drain readily. 

When the entire roadbed is somewhat damp or soggy it was 
formerly the general practice to lay a foundation of large stones 
wedged together by small stones and thoroughly rammed. This 
is called a Telford foundation and is 6 inches or more thick. 
It is still used extensively for the purpose but there are sub- 
stitutes for it which have come into use. In some cases from 
6 to 12 inches of coarse gravel or small field stone are placed 
on the subgrade and rolled. Still another type of drainage foun- 
dation, developed first in Massachusetts, is formed by excavating 
the subgrade to a V-shape cross-section, 6 to 8 inches deep 
at the sides and 12 to 18 inches deep at the center, and 
filling this with field stones, the largest at the bottom. With 
any of these types, there should be an outlet every 50 feet or so 
from the lowest part of the foundation, formed by cutting a 
trench through the shoulders to the side ditches and backfilling 
it with coarse gravel or stone. Even when the road is not on 
wet land, many engineers build cross drains filled with stones at 
50-foot intervals in the top of the subgrade of gravel and mac- 
adam roads. They are 5 or 6 inches deep at the center and 
are at right angles to the ditches except on hills, where they in- 
cline slightly downhill from the center. 

In many parts of the country stone or gravel is unavailable 
for such drainage work and drain tile has been employed. It 
has proved successful and economical, even when stone could be 
obtained, provided it was laid properly. Many engineers recom- 
mend using drains whenever water remains in the ground for a 
considerable period of time within 3 feet of the surface. The 
reason for this is that the maintenance of a well-drained road 
is easier work than if the subgrade is soggy. If a heavy rainfall 
soaks the top of a road which is already soft below the surface, 



28 AMERICAN HIGHWAY ASSOCIATION 

heavy loads are liable to rut it seriously, because it will take much 
longer to dry out than a well underdrained road. In the early 
spring, when the water in the ground freezes and thaws alter- 
nately, good underdrainage is particularly useful in preventing 
the upheaval of parts of the road. 

The influence of a well-laid line of drain tile upon the position 
of the upper surface of the ground- water, called the ''water table" 
by many engineers, is greater than many persons realize. Prof. 
Ira O. Baker has reported the following experimental proof 
of the extent of this influence. Lines of drain tile were laid 
50 feet apart and 2| feet deep in a field notoriously soggy 
and heavy on account of the presence of hardpan which held 
the water ''like a jug." Where the field was without drainage 
the water rose to within 6 inches of the surface. Where it 
was drained, the water level midway between the drains was 
18 inches below the surface, showing that even in such 
very heavy soil, the top surface of the ground-water 25 feet 
from the drain was only 1 foot above the tile. It is this wide 
influence of good drains which makes the effect of a single line of 
deep-laid tile along one side of a road greater than that of shal- 
low lines along both sides. The general rule of agricultural 
drainage experts is to place drains 100 feet apart and at a depth 
of 3i to 4 feet. 

The drain is best laid in a trench below the ditch at the side 
of the road from which the greatest amount of ground-water is 
expected. Although a large number of drains laid perfectly 
horizontal for long distances have given satisfactory service, it is 
desirable to give them a uniform slope of at least 2 inches per 
100 feet if possible. This is a somewhat lower minimum grade 
than some engineering books recommend, but is warranted by 
experience. The tile should not be smaller than 4-inch, and if 
the ground contains a large amount of water and the outlets 
of the drains are far apart, larger sizes may be desirable, partic- 
ularly in level country. 

Tile should not be laid except from grade lines given by the 
engineer, and they must be laid accurately to line and grade. 
The trench to receive them should be no larger than is necessary 
to lay them properly at the least expense, but in opening a trench 
it is sometimes less expensive to make it wider than required for 
the tile, because of the extra cost of digging in a very narrow 
trench. In any case the bottom should be cut very carefully 
so as to have it exactly on the right grade. If there is any prob- 
ability that the bottom will settle and throw the tile out of align- 
ment, a 4 by 1-inch plank is sometimes laid to support the 
tile. The ends of the tile are laid touching. Some engineers 
recommend covering the top half of the joint with tar paper or 



DRAINAGE, CULVERTS AND BRIDGES 29 

burlap, but this is probably unnecessary if the trench is back- 
filled with clean gravel or broken stone from 1 to 4 inches 
in size, which is the best material to use. In any case the fill- 
ing should be porous and placed carefully so as not to move the 
tile. When the gravel or stone filling is within 12 inches of 
the surface, some engineers cover it with about 3 inches of 
hay or straw before the earth filling is placed to form the bottom 
of the side ditch. 

The outlets of the drains should be constructed with special 
care, because they are particularly liable to injury. They are 
preferably made of stronger pipe than agricultural tile, firmly 
supported and protected at the end by a substantial wall or 
facing. A drain with its end stopped is of little value. 

Pipe drains are the most serviceable t^'pe, but there are vari- 
ous substitutes. One of these is a covered trough of rough stone, 
another is a similar plank trough, and another is merely a mass 
of gravel and stones, with the largest pieces at the bottom. The 
drawback of all of these is that they tend to break down or be- 
come clogged with fine material, which can not enter a properly 
laid tile drain. 

Where the side ditches are on very flat grades, they are some- 
times drained into the underdrains at intervals of about 0.1 mile 
by blind catch-basins. These are merely masses of coarse gravel, 
stone or brickbats reaching from the bottom of the ditch to the 
tile, and covered at the top by a low pile of similar material 
which acts as a screen. By this means the side ditches need 
not be cut so deep as to be dangerous. Where the side ditches 
carry large quantities of water which must be drained off in this 
manner, large drain tiles are needed and open brick or concrete 
inlets like those used on sewerage systems may be used. 

Where an embankment is built on a wet side hill, the latter 
must first be underdrained thoroughly to prevent slipping of the 
embankment. When an embankment in such a locality begins 
to slip, the trouble may sometimes be remedied by digging large, 
deep intercepting ditches on the high side, leading to the nearest 
culverts. These ditches are usually filled with stone. Any 
pockets in the ground near the uphill toe of the embankment, in 
which water may collect and soften the neighboring earth or clay, 
should be filled. 

Size of Culvert Openings and Bridge Waterways 

The waterway to be provided for large culverts and bridge 
openings depends upon many conditions, which have been stated 
as follows by Prof. A. N. Talbot: 



30 AMERICAN HIGHWAY ASSOCIATION 

1. The variation of the rainfall in different localities. 

2. The meagreness of rainfall data, since records are gener- 
ally given as so much per day and rarely per hour, while the du- 
ration of the severe storms is not recorded. 

3. The melting of snow with a heavy rain. 

4. The permeability of the surface of the ground, depending 
upon the kind of soil, condition of vegetation and cultivation, etc. 

5. The degree of saturation of the ground and the amount 
of evaporation. 

6. The character and inclination of the surface to the point 
where the water accumulates in the watercourse proper. 

7. The inclination or slope of the watercourse to the point 
considered. 

8. The shape of the area drained and the position of the 
feeders. 

The importance of this item will be seen in comparing a spoon- 
shaped area where the main watercourse is fed by branches from 
both sides so arranged that water from the whole area reaches the 
culvert at the same time, with a long, narrow basin in which, 
before the water from the upper part reaches the opening, the 
rainfall from the lower portion has been carried away and the 
severe part of the storm is past. 

While there are three formulas giving the size of waterways 
for drainage areas of different sizes, it is generally agreed by 
engineers that it is best to find out by examination and inquiry 
if possible the flood heights of any stream that is crossed. The 
condition of neighboring culverts and bridge openings during 
floods should be investigated, and the nature of the channel of 
the stream and the character of its drainage basin ascertained. 
Such records are not only helpful in determining the size of the 
structure under consideration but are of value in showing the 
degree of reliance that can be placed on a waterway formula. 

A formula widely used in the Central States was proposed in 
1887 by Prof. A. N. Talbot. The area in square feet of the net 
waterway is found by multiplying the three-fourths power of the 
acres drained by a coefficient. This coefficient was taken by 
Professor Talbot as 0.33 for rolling farming land subject to floods 
when snow melts and the valley drained is three or four times as 
long as it is wide, 0.16 to 0.2 in districts not affected by snow and 
with the valleys several times longer than wide, and from 0.67 to 
1.0 for steep, rocky ground. The waterways given by this for- 
mula are stated in the table on the next page. 



DRAINAGE, CULVERTS AND BRIDGES 



31 



Square Feet of Waterway Required by Talbot's Formula for Passing the Runoff 
from Areas Stated of Different Classes of Land 



ACRES 
DRAIN- 
ED 


LEVEL 
LAND 


ROLL- 
ING 
LAND 


HILLY 
LAND 


MOUN- 
TAINOUS 


ACRES 
DRAINED 


LEVEL 
LAND 


ROLLING 
LAND 


HILLY 
LAND 


MOUN- 
TAINOUS 


10 


1.1 


2.3 


3.4 


4.5 


180 


9.8 


19.7 


29.5 


39.3 


20 


1.9 


3.8 


5.7 


7.6 


200 


10.6 


21.2 


31.8 


42.5 


30 


2.6 


5.1 


7.7 


10.2 


240 


12.2 


24.4 


36.6 


48.8 


40 


3.2 


6.4 


9.5 


12.7 


280 


13.7 


27.4 


46.1 


54.8 


50 


3.8 


7.5 


11.3 


15.0 


320 


15.1 


30.3 


45.4 


60.5 


60 


4.3 


8.6 


12.9 


17.2 


360 


16.5 


33.1 


49.6 


66.1 


70 


4.8 


9.7 


14.5 


19.4 


400 


17.9 


35.8 


53.7 


71.6 


80 


5.4 


10.7 


16.1 


21.4 


440 


19.2 


38.4 


57.6 


76.9 


90 


5.8 


11.7 


17.5 


23.4 


480 


20.6 


41.2 


61.8 


82.3 


100 


6.3 


12.6 


19.0 


25.3 


520 


21.8 


43.6 


65.3 


87.1 


120 


7.3 


14.5 


21.8 


29.0 


560 


23.0 


46.0 


69.1 


92.1 


140 


8.1 


16.3 


24.4 


32.6 


600 


24.2 


48.5 


72.7 


97.0 


160 


9.0 


18.0 


27.1 


36.1 


640 


25.4 


50.9 


76.3 


101.8 



About 1880 the Santa Fe system began to measure accurately 
the area of the waterways of streams during floods in Missouri, 
Kansas, Indian Territory and Texas. The work was done as 
carefully as possible and in 1897 the results were summarized 
and a table of waterway areas issued by James Dun, chief engi- 
neer of the system, for the use of his engineers. The collecting 
of such information was continued after that date, and in 1906 
an enlarged table was printed for public use, which is extensively 
emiployed by railway and highway engineers in the section of the 

Square Feet of Waterway Given by Dun's Table for Passing the Runoff from 
Areas Stated; Applicable to Missouri and Kansas 



Area, square mile 

Waterway, square feet. 



Area, square mile 

Waterway, square feet. 

Area, square mile 

Waterway, square feet. 



Area, square mile 

Waterway, square feet. 

Area, square mile 

Waterway, square feet. 



Area, square mile 

Waterway, square feet. 

Area, square mile 

Waterway, square feet. 



0.01 
2.0 

0.10 
16 

0.55 
70 

1.0 
100 

1.9 
190 

3.6 
357 

6.0 

509 



0.02 
4.0 

0.15 
25 

0.60 
74 

1.1 
110 

2.0 
200 

3.8 
373 

6.5 
533 



0.03 
6.0 

0.20 
32 

0.65 

78 

1.2 

120 

2.2 
220 

4.0 

388 

7.0 
550 



0.04 
7.5 

0.25 
38 

0.70 
81 

1.3 
130 

2.4 
240 

4.2 
403 

7.5 
579 



0.05 
9.0 

0.30 
44 

0.75 
85 

1.4 
140 

2.6 
200 

4.4 
417 

8.0 
601 



0.06 
10.5 

0.35 
51 

0.80 
88 

1.5 
150 

2.8 
280 

4.6 
430 

8.5 
622 



0.07 
12.0 

0.40 
56 

0.85 
91 

1.6 
160 

3.0 
300 

4.8 
443 

9.0 
641 



0.080.09 



13.5 

0.45 
62 

0.90 
94 

1.7 
170 

3.2 
321 

5.0 
455 

9.5 
660 



15 

0.50 
66 

0.95 
97 

1.8 
180 

3.4 

340 

5.5 
483 

10.0 
679 



32 



AMERICAN HIGHWAY ASSOCIATION 



country mentioned. A portion of the table is reproduced here. 
Mr. Dun stated that it did not give waterways large enough for 
the floods that occurred at very long intervals and were of un- 
precedented severity, for which he did not consider it advisable 
for provision to be made. He recommended waterways 60 to 
80 per cent as large as those tabulated for culverts and bridge 
openings in Illinois, about 5 per cent larger waterways for Texas 
when the areas drained exceeded 1 square mile, and from 1 J to 6 J 
per cent smaller waterways in New Mexico for areas exceeding 
1 square mile. 

About thirty years ago, C. C. Wentworth, of the engineering 
staff of the Norfolk & Western Railway, made a careful study 
of the area of the culverts which had proved of sufficient size on 
that road, and found that for drainage basins of one acre and 
upward, the square feet of culvert cross-section should be equal 
to the two-thirds power of the number of acres drained. This 
formula has been used for many years on that railway and found 
entirely satisfactory. The accompanying table gives the areas 
computed by it for a number of drainage districts. These re- 
lations hold good quite generally over the area between the Blue 
Ridge and the Ohio River, and have been found to agree with 
flood discharges in Maine, Connecticut, and New York. It 
has been suggested that with rainfalls of less intensity or flatter 
slopes than those of the section which furnishes the data on which 
the formula is based, the areas of necessary waterways may be 
taken at some percentage of those given by the formula. 

Square Feet of Waterway Required to Discharge the Runoff from Areas of 1 
to 99 Acres, Computed by the Wentworth Formula 








1.0 


2.0 


3.0 


4.0 


5.0 


6.0 


7.0 


8.0 


9.0 







1.0 


1.6 


2.1 


2.5 


2.9 


3.3 


3.7 


4.0 


4.3 


10 


4.6 


4.9 


5.2 


5.5 


5.8 


6.1 


6.3 


6.6 


6.9 


7.1 


20 


7.4 


7.6 


7.9 


8.1 


8.3 


8.5 


8.8 


9.0 


9.2 


9.4 


30 


9.7 


9.9 


10.1 


10.3 


10.5 


10.7 


10.9 


11.1 


11.3 


11.5 


40 


11.7 


11.9 


12.1 


12.3 


12.5 


12.7 


12.8 


13.0 


13.2 


13.4 


50 


13.6 


13.8 


13.9 


14.1 


14.3 


14.5 


14.6 


14.8 


15.0 


15.1 


60 


15.3 


15.5 


15.7 


15.8 


16.0 


16.2 


16.3 


16.5 


16.7 


16.8 


70 


17.0 


17.2 


17.3 


17.4 


17.6 


17.8 


18.0 


18.1 


18.3 


18.4 


80 


18.6 


18.7 


18.9 


19.0 


19.2 


19.3 


19.4 


19.6 


19.8 


19.9 


90 


20.1 


20.2 


20.4 


20.5 


20.7 


20.8 


21.0 


21.1 


21.3 


21.4 



Culverts 

As the amount of water to be carried across the roadway by a 
culvert is usually small, the majority of such structures are made 
of some kind of pipe. The defects which such culverts develop 



DRAINAGE, CULVERTS AND BRIDGES 33 

at times are generally due to lack of attention to features essen- 
tial for good construction. The pipe must be laid on a perfect- 
ly firm support. If the trench for it is cut too low and must be 
leveled by replacing some of the material, the latter should be 
consolidated thoroughly before the pipe is laid, and as it takes 
considerable time to do this properly, it pays to be careful to 
excavate in the first place to the exact grade. ^ After the pipe 
has been laid and the joints filled if it is made of bell-and-spigot 
lengths, the backfilling should be done with the same care used 
in good sewerage work. The earth should be ramm.ed thorough- 
ly around the sides of the pipe, taking care not to disturb it in 
doing this, and not more than 6 inches of earth should be spread 
without ramming. The 2 feet of fill imm^ediately over the 
pipe should be similarly placed in 6-inch layers and rammed, 
and while the material above this need not be placed so carefully 
it should be thoroughly consolidated. 

The inlet and outlet of the pipe should be at the bottom of the 
ditches it connects or at the level of the bed of the brook that it 
carries across the road. Each end should have a wall or facing 
resting on an absolutely firm foundation far enough below the 
surface to remain unaffected by frost and heavy enough to hold 
back the bank resting against it. Concrete makes the best 
facing, but substantial masonry and heavy planks have given 
good service when properly used. By locating and protecting 
the ends of the pipe in this way two important advantages are 
gained, first, the thorough drainage of the side ditches and, 
second, the prevention of undercutting of the ends of the pipe. 
If the bottom of the ditch or bed of the brook is soft, it should be 
paved for some feet above and below the culvert to prevent 
serious erosion during severe storms. At irregular intervals 
several years apart the ditches and brooks are exceptionally 
flooded and the water is liable to rise above the top of the pipe. 
If the culvert has been constructed as just recommended no 
danger need be feared, for the road will act as a dam for a few 
hours until these excessive quantities of water are discharged. 
A poorly built culvert is likely to be washed out, however, and 
carry part of the road with it. Standard plans for culvert head- 
walls can be obtained from most State highway departments and 
from the United States Office of Public Roads and Rural Engineer- 
ing at Washington. 

Where a pipe culvert is carried across a side-hill road, dis- 
charging on the outer slope, some form of channel is often neces- 
sary for carrying the water down the side of the embankment 

^If the sub-grade is soggy it is well to lay the pipe on a concrote floor 
running from the foundation of one hcadwall to that of the other. Bell 
joints should be laid up-hill. 



34 AMERICAN HIGHWAY ASSOCIATION 

without causing erosion. Gutters of rough stone paving, con- 
crete channels and metal troughs have all been used for this 
purpose. 

When a culvert is formed of two pipes laid side by side, which 
is desirable where the grades are very flat, or the bed of the brook 
is wide and the depth of water shallow even after heavy rains, 
particular care must be exercised in consolidating the filling be- 
tween the pipes. 

In a few places, where timber is abundant and cheap, cul- 
verts of heavy planlc are used, but at the best, they are only 
temporary structures, and it is unwise to put temporary works 
which are costly to replace in a roadway graded to permanent 
lines. The same is true of box culverts of dry masonry, with 
unpaved bottoms. Masonry culverts laid carefully in cement 
mortar are rarely so cheap as permanent pipe or concrete cul- 
verts. Plans and instructions for building concrete culverts 
can be obtained on application from most State highway de- 
partments and from the United States Office of Public Roads 
and Rural Engineering. 

Any type of concrete culvert should be built carefully or 
frost will cause trouble with it. The sand and gravel or broken 
stone miust be clean and graded so as to give a dense mixture, 
and the mixing of the mortar must be thorough. The forms 
m.ust be strong and tight and located so that the structure will 
be true to grade. The headwalls in particular should be carried 
down to a secure foundation, and piling or a substantial tim^ber 
platform should be used to carry the concrete in case there is 
any doubt whatever of the supporting power of the underlying 
material. 

The general tendency of rapidly flowing streams is to lower 
their beds. This results in time in leaving the culvert floor 
rather high for the natural bed of the stream and the water finds 
its way underneath. A substantial cross wall at the outlet end of 
the culvert, carried well below possible wash, is effective in stop- 
ping this class of under-cutting, A frozen earth floor will som^e- 
tim.es act like a plank floor in causing such undercutting, and 
hence good cross-walls are advisable in all culverts, whether 
floored or not. If the channels leading to or from a culvert are 
in soft material liable to erosion, they should be paved or pro- 
tected by brush and heavy stones. 

Bridges 

Structures with a clear span exceeding 6 feet are generally 
classed as bridges and should be perm.anent improvements on any 
road brought to final grade and alignment. There has been 



DRAINAGE, CULyERTS AND BRIDGES 35 

such great waste of money in past years on the bridges on rural 
roads that the highway departments of most states have prepared 
standard plans and specifications which cover most needs of 
local road officials, and similar standards have been prepared 
by the United States Office of Public Roads and Rural Engi- 
neering. Structures of this character should only be built under 
competent engineering supervision, both as to substructures and 
superstructures. There is an unfortunate tendency on the part 
of highway commissions to endeavor to save money by omitting 
desirable precautions such as piling, which insure the safety of 
the bridges under conditions which an engineer recognizes as 
dangerous. For example, an unusually heavy rainfall in north- 
eastern Iowa in June, 1916, washed out 163 bridges. Some were 
old structures that needed replacing at an early date, but others 
were expensive new structures of good design and construction 
except for the fatal omission of the piling under the founda- 
tions which was recommended by the engineers but left out to 
reduce the cost. Not a bridge built according to the standards 
of the State highway commission was damaged. 

There are many bridges which have been in service for a long 
period of time without suffering any injury, although their sub- 
structures are in streams with an easily eroded bottom and banks. 
For example, the Walhouding aqueduct on the Ohio canal system, 
built about 1830, has four piers and two abutments in a stream 
with a fairly swift current, rising suddenly to a great height. 
Both its banks and bed near the aqueduct are rapidly eroded 
unless protected. The piers and abutments rest on double plat- 
forms of hewn timbers, laid crosswise and carried by piles driven 
close together near all four sides of each base. Brush and heavy 
stone were placed on the river bed around each foundation and 
a row of strong piles was driven across the river bed just below 
the aqueduct to prevent the removal of the brush and stones by 
the current. Such a record of endurance made by structures 
built before the beginning of the present era of scientific engi- 
neering shows how needless are most of the washouts of expen- 
sive bridges that occur every year. 

As bridges on improved roads should be permanent struc- 
tures, they should be designed to carry a heavy roller followed 
by a trailer loaded with coal. A bridge capable of supporting 
a 15-ton roller will carry any of the heaviest field guns now 
used in Europe. 

Money is saved by having the plans and specifications for 
bridges of reinforced concrete or steel prepared by an expe- 
rienced engineer, so that all bidders on its construction will base 
their estimates on the same structure and that structure will be 
adapted to the locality and ser^nce. If each bidder must prepare 



36 AMERICAN HIGHWAY ASSOCIATION 

his own plans, the expense of doing so is added to the cost of the 
fabrication of the steel and the erection of the structure. This 
makes a general increase in the cost of bridges in a district where 
the practice is followed, for many unsatisfactory plans must 
be prepared for one that is satisfactory. Furthermore the com- 
mission awarding the contract must not only pick out the lowest 
bidder but also decide which is the best plan, which may not 
be that offered at the lowest price. 

In level country where a stream overflows its banks during 
heavy floods and bridges above the flood level require long expen- 
sive approaches, what are known as overflow bridges are coming 
into quite extensive use. They are structures designed to be 
submerged by the floods and to offer as little obstruction as pos- 
sible to the water passing over them. If the floods are likely 
to carry large quantities of brush, the bridges are kept partic- 
ularly low so the brush will pass freely over them when they are 
submerged. The roads leading to a number of such bridges 
have concrete pavements extending to the limits of the sub- 
merged areas, for earth, gravel and broken stone roads are liable 
to serious injury from water flowing across them. As the injury 
to overflowed embankm^ents generally starts at the top of the 
downstream, slope, the latter is often protected against scouring 
by covering it with heavy stone. Stone with rounded edges is 
less suitable for this purpose than stone of an angular shape, 
because the former is rolled about more easily. 

Fords 

Where money is limited, the cost of building even a submerged 
bridge is heavy, and the stream to be crossed is shallow, a ford 
is sometimes constructed as a serviceable temporary expedient. 
In Washington County, Utah, for example, there is a stream with 
a sandy bottom which is dry at some seasons and dangerous 
during floods on account of the treacherous nature of the wet 
sand. A ford has been constructed which consists of two rubble 
walls 4 feet deep and 2 feet wide, with a 2-foot rubble fill between 
them. The entire width of this rubble fill from one wall to the 
other is 20 feet, and the stones of which it is made were laid in 
a dense mixture of sand and clay, which is not easily washed out 
of the voids between the stones. The upstream wall was laid 
dry but had 16 inches of clay puddled against the entire depth 
of its outer face. The downstream wall was laid in lime mortar. 

Near Shelbyville, Tennessee, fords have been made passable 
at all times by constructing a number of parallel culverts close 
together to carry the usual flow of the stream and building a 
concrete roadway over these culverts to give a safe footing for 
horses and a secure roadway for automobiles during high-water 
when the roadway is submerged. 



EARTH AND SAND-CLAY ROADS' 

As a very large proportion of our country roads must be earth 
roads for many years and the basis for any t>T)e of surfaced high- 
way is a properly located, drained and graded earth road, the rela- 
tive importance of this t>'pe is very great. If earth roads were 
properly constructed and maintained, and their culverts and 
bridges were permanent structures, a large part of the road taxes 
now wasted would produce useful returns. It is proper for both 
highway commissions and engineers to devote a large part of 
their time and money to the improvement of the main roads 
which are of service to the largest number of taxpayers, but there 
is a deplorable lack of efficiency in the care of the local dirt roads in 
many parts of the country. In some States, of which New York, 
Illinois and Iowa are examples, these roads are under some super- 
vision, directly or indirectly, by the State highway department, 
but generally the local authorities do as they please. For in- 
stance, in 1916 there were 71,000 miles of roads in Wisconsin in 
sole charge of local officials, who spent about $4,500,000 on them. 
The work was subdivided among nearly 13,000 road districts, 
each with a road supervisor, and there were 3750 members of town 
boards with general control over road work. Of these 16,750 
officials, about one-fifth drop out of office annually. During 
the ten years ending December 31, 1916, nearly' 50,000 men 
were in charge of local road work and over $40,000,000 spent by 
them, with few perceptible lasting improvements. A system 
giving such results is manifestly wrong, and should be replaced 
by one with a smaller number of road officials having greater 
authority and responsibilities and serving longer terms. It will 
seem from the following notes that the construction and mainte- 
nance of earth roads calls for executive ability and skill that can- 
not be obtained unless fair permanence in office is assured. 

The construction of earth roads falls into two general classes, 
that where there are cuts and fills and that where the road is 
formed by building a low embankment on the surface. Except 
where the length of road is great enough to use elevating graders 
with economy, these two classes are generally built by different 
methods. 

* Revised by W. S. Keller, State Highway Engineer of Alabama. 

37 



38 AMERICAN HIGHWAY ASSOCIATION 

Cuts and Fills 

In grubbing roots and breaking hard ground to a shallow depth, 
a rooter plow is often used, which is a heavy type of subsoil plow 
made for the purpose. The road plow is a heavy form of turning 
plow used in hard ground where the cuts are shallow. Either 
type is drawn by four to eight horses or a tractor. Plows are 
also specially made for pushing soil already loosened from ditches 
toward the center* of the road. 

When the cut is more than a few feet in depth and the mate- 
rial loosened with difficulty, it is often blasted. The fastest and 
most economical method of doing this is to sink holes across the 
cut on a line back from the face a distance about one-fourth 
greater than the depth of the cut and about the same distance 
apart. When the cut is 6 feet or more deep, the line of holes 
is kept about 6 feet from the face and the holes are sunk about 
6 feet apart. They are loaded with a low-strength explosive 
and care must be taken not to loosen the ground below the fin- 
ished grade line. The use of explosives in road grading in other 
m-aterial than rock has been extending rapidly on account of its 
low cost and the rapid progress that can be made under suitable 
conditions, for the blasts leave the clay or hardpan in a broken 
up condition m^aking it easy to handle. On side-hill cuts in heavy 
ground, where the slope is steep and there is some question about 
the security of an embankment to carry the outer part of the 
road, a safe roadway can often be blasted out of the hill at a cost 
comparing favorably with a road partly supported by a retain- 
ing wall. Even on easier slopes, where a long side-hill cut in 
heavy ground must be made and the excavated material can be 
employed as an embankment to carry the outer part of the road- 
way, the excavation is often made by blasting. Blasting is 
also an effective method of breaking up stumps and boulders. 

Where the material is easily handled and can be dumped within 
100 feet of the cut, slip scrapers are generally regarded as the 
least expensive equipment. The Fresno scraper is regarded as 
better than the slip scraper for hauls exceeding 100 feet. If the 
haul exceeds 100 feet and is under 1000 feet, wheel scrapers are 
ranked highly. The large sizes are m.ost desirable for econ- 
om-y on hauls over 600 feet. The material is usually plowed so 
the wheelers can be loaded easily, and it is necessary to have 
about one of them for every 100 feet of haul in order to work 
most economically. Bottom-dump wagons can be made to give 
very low hauUng costs if enough are provided so that while one is 
being loaded at the cut, the driver and team which brought it in 
can be used in hauling a loaded wagon. 

In recent years traction steam shovels have been growing stead- 



EARTH AND SAND-CLAY ROADS 39 

ily in favor for road grading. They make shallow cuts as easily 
as deep cuts, and have taken out earth and rock at very low 
figures when the equipment for removing the excavated mate- 
rial was properly selected and used so as to keep the shovel work- 
ing most of the time. The economy of steam shovel operation 
depends upon the proportion of the working day that it is ac- 
tually digging, and this depends upon having wagons or cars 
ready to receive the excavated material. The wagons or cars 
may often be run along the top of the bank of a shallow cut 
and kept moving in a continuous line, saving the delay of turn- 
ing and backing up to the shovel, which is necessary when 
they move over the graded cut. The utility of a shovel on road- 
work is increased if it can be employed in a gravel pit or quarry 
when not grading. 

The bottom of the cut should be carried down approximate- 
ly parallel to the finished cross-section, and care should be taken 
not to disturb the material below the grade line. In very heavy 
ground, the final trimming is sometimes done by hand, but gen- 
erally a road machine can be used to advantage. 

Where a fill is made, the surface must be cleared. Stumps 
should be grubbed out^ and all large material liable to decay 
should be removed, for if left in place the fill will settle as it rots 
or have loose places likely to retain moisture. If the fill is on 
a steep side-hill, the latter should be cut into a series of level 
benches or steps and the drainage should receive careful atten- 
tion. If the hill has a gentle slope, it is usually suflicient to plow 
parallel furrows, which will furnish a sufficiently uneven surface 
to hold the fill. The object in any case is to unite the material 
in the bottom of the embankment with that of the hillside. 

If the road will be maintained as an earth road for several 
years, so it will have ample time to become consolidated under 
traffic before any surfacing is applied, there is usually little rea- 
son for limiting the thickness of the layers in which the embanlc- 
ment is built. But if a surfacing is to be given the road at an 
early date, the layers should not exceed 2 feet for high fills and 
1 foot for low fills. The teams and scrapers moving over the 
fill compact it to some extent. Formerly little attention was 
paid to smoothing the surface of the layers, but of late this has 
been considered important in some states and drags are kept 
at work on a bank a large part of the time. George W. Cooley, 
State engineer of Minnesota, has explained this leveling work 
as follows: 

^ It is not customary in the South to require green stumps and roots to 
be grubbed where the fill over their tops is as much as 18 inches. Any 
matter in process of decay must be removed but a green stump sealed in a 
fill so that air will not reach it lasts forever. 



40 AMERICAN HIGHWAY ASSOCIATION 

In Minnesota the plan has been adopted in the construction of earth 
roads to require the continual use of a drag or planer on grade building. 
This latter plan has been found very efficient and renders future work on 
the surface less expensive, besides tending to produce a more compact 
road bed. The tool found most satisfactory in this work is that known 
as the "Minnesota road plane," which consists of the two blades of an ordi- 
nary road drag, fixed between a pair of runners about 14 feet long, the blades 
set at an angle of about 60 degrees to the runner and made rigid or adjust- 
able as may be deemed best. The planer is hauled on a line parallel with 
the axis of the road and its operation is similar to that of the ordinary drag, 
with the additional advantage of making a smoother surface. The old 
style drag without runners has a tendency, especially on new work, to 
increase the waves or undulations frequently occurring on road construc- 
tion, while the planer eliminates these faults and as a general maintenance 
tool has proved the most satisfactory. 

All embankments settle or ''shrink" for some time after they 
have been built. If the material is broken into small pieces and 
trampled by teams, the shrinkage will be less than if it is dumped 
in large masses. There is little shrinkage in a well-built earth 
dam to impound water, but road embankments need not be 
built so carefully, and it is probably desirable to allow for at 
least 10 per cent shrinkage of embankments over 3 feet high and 
at least 15 per cent for those under 3 feet. If loamy material is 
used in the embankments the shrinkage will probably be greater 
than this. 

Grader Work 

A large part of the earth roads now built or reconstructed are 
made with road machines. These are built in many sizes for 
both horse and tractor hauling, and serve a variety of purposes 
in an economical manner. They are not adapted for making 
cuts and fills, although frequently employed in shaping a road 
after the grading has been done. The method of using the 
machine on construction is explained in the following instruc- 
tions prepared by W. S. Gearhart, State engineer of Kansas: 

In building new roads with a road grader the dead weeds and grass 
should first be burned off before any grading work is done, and the width 
of the road to be graded should be staked so the ditches can be properly 
lined up. Then plow a light furrow with the point of the grader blade, 
carrying the rear end of the blade well elevated.^ On the second round 
drive the wheels in line with the point along the hollow made the first 
round, plowing a full furrow with the advance end of the blade, dropping 
the rear end somewhat lower than before. The third time mova toward 
the middle of the road the earth previously plowed, then return to the 
ditch and plow it out deeper, moving the earth toward the middle when- 
ever as much has been plowed as the machine will move at once. Repeat 
this process until the ditches are the proper depth, and then cut ofif the 
outer slopes of the ditches by placing one wheel of the grader in the bot- 
tom of the ditch and the other one on the bank. This can be done easily 

^ A plow is necessary in breaking up the ground except in light soils. 



EARTH AND SAND-CLAY ROADS 41 

if the bank is not more than 30 inches above the bottom of the ditch. Then 
trim the earth to the true cross-section. Thoroughly harrow the loose 
material with an ordinary straight-tooth harrow if there are no clods, goinj' 
over it until the bumps have been leveled off, the low places filled up and 
the material well compacted. If there are sods or tough lumps of earth 
in the road a disk harrow should be used to pulverize this material, and 
the disk harrow should be followed by a drag or a straight-tooth harrow 
to level and smooth the road. No newly graded road can be finished in 
good shape without using either the harrow or the drag, or both. 

In the later rounds of a road machine, in the final shaping 
of the road, part of the loose material in the center of the road 
is pushed back to the shoulders. The settlement on fills will 
result in losing about 2 feet in the width of the roadway, and the 
fills should be made wider than the standard sections to allow 
for this loss. In doing this final w^ork, the blade of the grader 
is set at an angle of about 45 degrees with the direction of travel, 
its ends adjusted to the slope of the road, and lowered as a whole 
on successive rounds. 

If the work is on a scale large enough to warrant the use of two 
graders hauled by a tractor or roller, a trained grading crew is 
often able to build a good roadbed at very low cost. Mechani- 
cal traction has resulted in the development of methods of con- 
struction impracticable when teams of four to eight horses were 
employed, and as a general proposition mechanical traction is 
most economical when the sections to be graded are a quarter 
of a mile or more long, and there is enough work in the vicinity 
to keep a tractor busy most of the time.^ Time lost in standing 
idle or moving long distances from one grading job to another 
reduces the economical advantage of a tractor on work not well 
organized. In many cases the hauling is done by a road roller. 
Tractors and rollers are particularly good investments where 
labor and teams are hired at high rates and not always obtainable. 
Mechanical traction is so much more powerful and rapid than 
horse traction, that its total saving on road work can only be 
figured by including the saving in labor charges due to speedy 
construction. 

Where road grading is carried on by day labor by district offi- 
cials, preparation is sometimes made for it in late fall or early 
spring by plowing up the ground along the lines of the ditches 
and slopes. This disintegrates the sod and prevents the roots 
of grass and weeds from forming clods which must be broken 
up by disk harrows or thrown out of the road with forks. While 
it is allowable to build an embankment on good sod after it has 
been burned over, neither sod nor any other organic material 

^ Traction grading with heavy road machines is better adapted for some 
conditions than others, and the advice of an experienced engineer should be 
obtained before purchasing expensive equipment 



42 AMERICAN HIGHWAY ASSOCIATION 

should be allowed in the embankment unless reduced to small, 
disconnected bits. If clods are left in a fill, particularly in the 
top, it is very difficult to maintain by dragging a hard, uniform 
surface free from depressions and waves. 

Grading by machines is often followed up immediately by 
hand trimming and the removal of loose stone. Easing upon 
work by leaving steep, untrimmed slopes and uneven ditches 
results in heavier maintenance expense. 

In organizing grader work, it is desirable to keep on hand re- 
pair parts of the macliines, such as blades and whiffletrees, as 
well as plow points and other parts of the equipment likely to 
wear out. The small tools should be selected with care, for 
observation by efficiency specialists has shown that the shape 
of a shovel, for example, has considerable effect on the amount 
of shoveling a man can accomplish in a day. Hard earth cannot 
be dug economically by the shovel best adapted for loose earth, 
and neither is best for gravel and broken stone. 

On extensive work the elevating grader has proved an eco- 
nomical and rapid machine when a mile or more of road can be 
traversed without turning the outfit. Such a grader is often 
hauled by a traction engine, which rolls the material it passes 
over and thus assists materially in making a compact road. The 
method of using the grader depends upon the nature of the work 
to be done. In cuts, the grader often discharges the excavated 
material into wagons driven beside it until full. These wagons 
haul the material to the nearest fills. In light cuts, the material 
is deposited on the roadway and moved to the nearest low places 
in the road by slip or wheel scrapers. The cut is usually started 
at the shoulder and the grader moves toward the roadside on 
successive rounds, so that the excavated material is deposited 
nearer and nearer to the center of the road by the elevating and 
discharging device. The road should be dragged during con- 
struction, and as soon as the rough grading is finished it should 
be shaped at once. In this connection attention is called to 
the following comment by the Iowa highway commission: 

The impassable condition to which some contractors and county road 
crews reduce their roads while cuts, fills and other improvements are being 
carried out, is absolutely inexcusable. The worst conditions usually 
arise at leveling or smoothing up while dumping is in progress. The dirt 
of the fill so dumped packs in humps so that sometimes it is impracticable 
to eradicate the unevenness for years. A little care in spreading the dirt 
evenly at the time of dumping results in the fill packing in thin, even lay- 
ers instead of humps. Such a road is travelable during construction, 
and when the fill is completed the job is done. A Marshall County road 
crew solved the problem by keeping a light road drag at hand. From time 
to time a team was unhooked from a scraper and hitched to this. A few 
minutes work put the freshly dumped material into thin layers instead 
of humps. 



EARTH AND SAND-CLAY ROADS 43 

The utility of a road roller on earth roads is generally under- 
estimated. After the earth has been given as much crown as 
the road can have and still enable the traffic to use its entire sur- 
face readily, any further improvement of the surface drainage 
must be attained by decreasing the porosity of the earth. This 
can be done by oiling the road as described later in the section 
on Surface Applications, and by reducing the pores of the earth 
by rolling. The latter is particularly useful in compacting places 
of a yielding character. Many counties have purchased rollers, 
placed them in charge of competent men, and rent the outfits 
to the townships as the latter need them. In some cases, a roller 
is bought by a number of townships, acting as a whole. The 
work of a roller outfit is likely to be unnecessarily expensive if 
it is not carefully planned so as to avoid long journeys to do small 
jobs. 

Dragging 

Earth roads under light traffic can be kept in good condition 
during a large part of the year by dragging and proper care of 
the ditches. It is an axiom in road maintenance that defects 
in the surface of a road should be remedied as soon as they 
appear, because traffic will develop them quickly. The earth 
road is particularly subject to injury because it does not have 
hard stone locked in place to resist the destructive effect of horses' 
shoes, narrow tires and pneumatic tires. On the other hand it 
is more easily repaired than any other road, because as soon as 
its surface is wet by rain the ruts and holes can be filled by haul- 
ing a drag over the surface. This scrapes material from the 
high points into the depressions and rubs down the whole sur- 
face. The following explanation of the nature of the improve- 
ment has been given by A. R. Hirst, State highway engineer 
of Wisconsin: 

If a sample of moist earth is taken from the traveled portion of a road 
over a gumbo, clay or black prairie soil, it will be found practically imper- 
vious to water, as may be proved by forming a roughly shaped dish of damp 
earth and filling it with water. It will be noticed that the dish is practi- 
cally water-tight. Earth in this condition is what the clay workers call 
puddled. It has been worked and reworked by the carriage wheels and 
animals' hoofs until nearly all the traveled portion of a sticky muddy 
road is covered with a layer of this impervious, puddled earth. As usually 
found on most of the roads, this puddled earth is full of holes and ruts, 
which are filled with water that cannot escape through the impervious 
soil. As long as the water remains the soil cannot dry out and the road 
is kept in a most uncomfortable if not impassable condition. It is also 
a matter of observation that this puddled earth when compressed and dried 
becomes extremely hard. On these two facts, the imperviousncss of pud- 
dled earth and its hardness when dried, rests the theory of road dragging. 



44 AMERICAN HIGHWAY ASSOCIATION 

When the road drag is properly used it spreads out the layer of imper- 
vious soil over the surface of the road, filling up the ruts and hollows until 
a smooth surface is secured. As a small amount of material is always to be 
pushed to the center, a slightly rounded effect will be given to the road, 
which may be increased or decreased as desired by subsequent dragging. 
By forcing the mud into the hollows and ruts it is evident that the water 
must go out, which it does by running off to the side of the road. The 
drying out of the road is thus much facilitated and the road is made imme- 
diately firmer because the water is squeezed out. The effect of traffic 
over the road tends to press down and thoroughly compact each thin 
layer of puddled earth which the drag spreads over the surface every time 
it is used. After the first few draggings it will be noticed that the road is 
becoming constantly smoother and harder so that the effect of a rain is 
scarcely noticeable, the water running off the surface which is so smooth 
and hard as to absorb but little of it. 

The drag is an old implement. It was described in a book by 
William Gillespie published in 1851 and widely used by stu- 
dents of engineering and public officials, yet the drag did not 
come into favor until about 1900. Even today it is not used on 
more than a small percentage of the roads where it should be 
em-ployed regularly. It has a number of forms, the essential 
feature being two parallel blades held vertically or nearly so 
about 2 J feet apart by a frame of some sort. The bottom of 
each blade scrapes over the surface of the road. The rear blade 
projects 12 to 16 inches to one side of the front blade so that 
when the drag is pulled at an angle of 30 degrees, the ends of the 
blades will be on a line parallel with the center of the road. The 
drag is hauled by a chain, to which the team can be hitched at 
points that will make the drag lie diagonally on the road as it is 
pulled along. The manner of its use has been described sub- 
stantially as follows by the United States Office of Public Roads. 

Under ordinary circumstances the position of the hitching link on the 
draw chain should be such that the runners will make an angle of from 
60 degrees to 75 degrees with the center line of the road, or in other words, 
a skew angle of from 15 degrees to 30 degrees. It is apparent that by 
shifting the position of the hitching link the angle of skew may be in- 
creased or diminished as the conditions require. When dragging imme- 
diately over ruts or down the center of the road after the sides have been 
dragged, it is usually preferable to have the hitching link at the center of 
the chain and to run the drag without skew. When the principal pur- 
pose of the dragging is to increase the crown of the road, the drag should 
DC sufficiently skewed to discharge all material as rapidly as it is collected 
on the runners. On the other hand, if depressions occur in the road sur- 
face, the skew may perhaps be advantageously reduced to a minimum, thus 
enabling the operator to deposit the material which collects in front of the 
runners at such points as he desires by lifting or otherwise manipulating 
the drag. It is impracticable to prescribe even an approximate rule for 
fixing the length of hitch, because it is materially affected by the height 
of the team and the arrangement of the harness, as well as by the condi- 
tion of the road surface. Experience will soon teach the operator, however, 
when to shorten the hitch in order to lessen the amount of cutting done 



EARTH AND SAND-CLAY ROADS 45 

by the front runner and when to lengthen it in order to produce the oppo- 
site effect. Care should be taken that a ridge, often called a "potato 
ridge," is not left in the center of the road. 

When the road surface is sufficiently hard or the amount of material 
which it is desired to have the drag move is sufficient to warrant the oper- 
ator standing upon the drag while it is in operation, he can greatly facili- 
tate its work by shifting his weight at proper times. For example, if it is 
desired to have the drag discharge more rapidly, the operator should move 
toward the discharge end of the runners. This will cause the ditch end 
of the runners to swing forward and thus increase the skew angle of the 
drag. The operator may, of course, produce the opposite effect by moving 
his weight in the opposite direction. In the same way, he can partially 
control the amount of cutting which the drag does by shifting his weight 
backward or forward, as the case may be. 

The rule frequently cited, that all earth roads should be dragged 
immediately after every rain, is in many cases entirely imprac- 
ticable and is also very misleading because of the conditions 
which it fails to contemplate. It is true that there are many 
road surfaces composed of earth or earthy material which do 
not become very muddy under traffic, even during long rainy 
seasons, and since such surfaces usually tend to harden very 
rapidly as soon as the weather clears up, it may be desirable to 
drag roads of this kind immediately after a rain. Such roads, 
however, would not ordinarily need to be dragged after every 
rain, because of the strong tendency that they naturally possess 
of holding their shape. On the other hand, many varieties of 
clay and soil tend to become very muddy under only light traffic 
after very moderate rains, and it is evident that roads constructed 
of such materials could not always be successfully dragged imme- 
diately after a rain. Sometimes, in fact, it may be necessary 
to wait until several consecutive clear days have elapsed after 
a long rainy spell before the road is sufficiently dried out to keep 
ruts from forming almost as rapidly as they can be filled by drag- 
ging. In many cases of this kind, however, it is possible greatly 
to improve the power of the road to resist the destructive action 
of traffic during rainy seasons by repeatedly dragging it at the 
proper time. 

Maintenance by dragging is most successful when well organ- 
ized. The results obtained by good management in Hopkins 
County, Kentucky, are frequently cited as indications of this, 
and for this reason the following account of the work there is 
quoted from a report by the Kentucky department of highways. 

In 1912 a county engineer was appointed. The county roads were 
measured under his supervision and 2-mile section^ designated, and in 
January, 1913, drags were started on about 100 miles of the county roads. 
This original contract was only for dragging the roads, which work was 
to be done four times between January 1 and April 1, at a cost of SIO to 
S12 per mile. As the sections dragged were not continuous, the citizens 



46 AMERICAN HIGHWAY ASSOCIATION 

at once appreciated the difference between the maintained road and that 
which was not maintained. Consequently the next contract, which 
called fordraggingandalsofor cleaning the ditches for six months, until 
November, 1913, resulted in contracts for 150 miles of road and at a re- 
duced cost. In November, 1913, a contract substantially like that now 
in use was adopted and the time of the contract was for one year, or until 
November, 1914. Over 200 miles were maintained this year at an average 
cost of $28 per year per mile. For the year from November, 1914, to No- 
vember, 1915, the benefit of the maintained roads was so well understood 
by the citizens that 560 miles were under contract at an average cost of 
$24.35 per mile per year. 

In November, 1915, a two-year contract was entered into, which the 
county may revoke for non-performance of the obligation at the end of 
the first year. About 520 miles are now under contract, at prices ranging 
from $12 to $40 per mile per year, the average being $22. 10. It is expected 
this mileage will soon be increased. Originally a contractor was allowed 
to have charge of 8 miles, but now he is not allowed to contract for more 
than 4 miles of road. Under the 1915 contracts the contractor must trim 
the branches which overhang and interfere with travel on the roadway; 
keep the roadway between ditches free from shrubbery and weeds; keep 
the ditches clean, free from obstructions, and at all times capable of car- 
rying the water. "He shall by June 1 each year grade the roads with dump 
scraper, grader, drag and ditcher, or in any way he may see fit, so that the 
center of the roadway shall be crowned so that the water will flow from the 
center of the road to the side ditches, and at no place will the water stand 
on the road or run down the road. The road shall be dragged from ditch 
to ditch at each dragging, when the road is wet, but not sticky." 

A record of the number of draggings is kept by the county engineer 
on cards which, before mailing by the contractor, are countersigned by the 
rural route carrier or a reliable citizen. The contractor also hauls ma- 
terial and constructs all culverts and bridges of 10-foot span or under, and 
keeps the approaches to and the floors and abutments of all bridges and 
culverts on his road in good traveling condition. An analysis of these 
contracts shows that where the contract has been faithfully executed 
there is a decrease each year in the cost per mile, mainly because the far- 
mer contractor has learned from experience that continuous maintenance 
makes a lower cost of time and labor each succeeding year. 

In the semi-arid regions, the soil is often of a very light nature, 
so lacking in adhesive qualities that strong winds or flowing 
water erode it and travel abrades it rapidly into fine dust. It is in 
its best condition to carry travel when it is moist, but if it be- 
comes saturated with water it is almost impassable. Chuck 
holes a foot deep are formed in dry weather in an earth road 
through such soil, and as they become filled with light dust they 
are a serious impediment to easy travel. Clay or gravel con- 
taining clay improves the roads when worked into them. The 
ditches should be wide and shallow, rather than deep, and the 
crown should be rather low for an earth road, in order to retain 
moisture in the roadbed. For the same reason, all grading and 
ditching are best done just before or during the rainy season, 
in order to have plenty of water to pack the soil. On account 
of the pulverulent nature of the material, the ends of all culverts 



EA.RTH AND 8AND-CLAY ROADS 47 

must be planned carefully and riprap or some other material 
placed to prevent erosion about the inlets and outlets. The main 
problem with earth roads in such soils is to keep the roadbed 
damp and to incorporate with it adhesive or fibrous material 
which will act as a binder. 

Sand-Clay Roads 

The grains of which sand is composed are usually hard and 
tough and able to resist abrasion if held securely in place. In 
an asphalt pavement they are held by the asphalt and a wearing 
surface of great resistance to abrasion results. In a sand-clay 
road they are bound together by clay in a less firm manner but 
one giving excellent results on well-drained roads carrying light 
traffic. The aim of the builder of such a road is to employ just 
enough of the stickiest clay at his command to fill the pores of 
the sand and to mix these materials together so thoroughly that 
there are neither lumps of clay nor pockets of loose sand left in 
the surfacing. This gives the maximum amount of hard sand 
to carry the trafiic and the minimum amount of clay to bind it. 
More sand makes a less durable road and more clay makes one 
which becomes soft more rapidly when wet. 

There is a great difference in the value of different clays for 
such work. Some of them become dough-like when mixed with 
a certain amount of water and can be molded into objects which 
retain their shape after drying. If these molded objects are im- 
mersed in water they will retain their form for a long time. These 
varieties are called ''plastic clays" and the most plastic are 
called ''ball clays." There are other varieties which fall to pieces 
more or less quickly when wet, as quicklime does, and they are 
therefore called "slaking clays." They are more easily mixed 
with sand than the plastic clays but they have much less bind- 
ing power and a road built with them is less durable when dry 
and more easily rutted when wet. The amount of clay to be used 
can be determined by a simple field test described as follows 
by Andrew P. Anderson: 

From typical samples of each of the available clays, test mixtures, 
varying by one-half part, are made with the sand so that each clay is rep- 
resented by a set of mixtures ranging by successive steps from one part 
sand and three parts clay to four parts sand and one part clay. Tnese 
are worked up with water into a putty-like mass and from each mix 
two equal quantities are taken and rolled between the palms of the hands 
into reasonably true spheres, labeled and placed in the sun to dry. When 
thoroughly baked, a set of spheres representing any one clay is placed in 
a flat pan or dish and enougn water poured gently into the pan to cover 
them, care being taken not to pour the water directly on the samples. Some 
samples wiU begin to disintegrate immediately. Those breaking down 



48 AMERICAN HIGHWAY ASSOCIATION 

most slowly contain most nearly the proper proportion of sand and clay 
for the particular materials. The relative bmdmg power of the various 
clays may then be determined by comparing the hardness and resistance 
to abrasion of the various dry samples having the correct proportion of 
sand and clay, as determined by the water tests. 

In February, 1917, representatives of 21 state highway depai't- 
ments and of the U. S. Office of Public Roads recommended the 
following mixtures for hard, medium and soft classes of sand-clay 
roads. 

Hard class: Clay, 9 to 15 per cent; silt, 5 to 15 per cent; total 
sand 65 to 80 per cent; sand retained on a 60-mesh sieve, 45 to 
60 per cent. 

Medium class: Clay, 15 to 25 per cent; silt, 10 to 20 per cent; 
total sand, 60 to 70 per cent; sand retained on a 60-mesh sieve, 
30 to 45 per cent. 

Soft class: Clay, 10 to 25 per cent; silt, 10 to 20 per cent; 
total sand, 55 to 80 per cent; sand retained on a 60-mesh sieve, 
15 to 30 per cent. 

By clay is meant material separated by subsidence through water 
and possessing plastic or adhesive properties; it is generally below 
0.01 mm. in diameter. By silt is meant the fine material other 
than clay which passes a 200-m.esh sieve and is generally from 0.07 
to 0.01 mm. in diameter. By sand is meant the hard material 
which passes a 10-mesh sieve and is retained on a 200-mesh sieve, 
and is generally from 1.85 to 0.07 mm. in diameter. 

The larger part of the following explanation of the construc- 
tion of sand-clay roads was prepared by W. S. Keller, State 
engineer of Alabama, where many miles of sand-clay roads have 
been built and are giving good satisfaction: 

Every farmer who lives in a section of country where both sand and 
clay are prevalent, is more than likely traveling over a section of natural 
sand-clay road but is ignorant of the fact. He can call to mind some 
particular spot on the road he travels, though it may not be more than 100 
feet in length, that is always good and rarely requires the attention of the 
road hands. Good drainage will be noticed at this place and if he takes 
the trouble to investigate, he will find that a good mixture of sand and 
clay forms the wearing surface. If this 100 feet of road is always good 
then the entire road can be made like it provided man will take advantage 
of the lesson taught by nature and grade the road so that the drainage 
will be good and surface the balance of the road with the same material. 
If it is not possible to find this ready mixed surfacing material convenient 
to the road it may be possible to find the two ingredients in close proximity. 
In case the road after grading shows an excess of sand, clay should be 
added, or in case clay predominates, sand should be added to produce 
good results. There are four general ways in which sand-claj'' roads may 
be built: 

1. Ready mixed sand and clay placed on clay, sand or ordinary foun- 
dation. 

2. Sand and clay placed on soil foundation and mixed. 



EARTH AND SAND-CLAY ROADS 49 

3. Clay hauled on a sand foundation and mixed with the sand, 

4. Sand hauled on a clay foundation and mixed with the clay. 
Taking up the various methods in order: 

1. A natural mixture of sand and clay can often be found where the 
two materials are found separate. The most important point is to know 
the natural mixture when seen. The very best guide to this is to find a 
natural piece of good road. A sample from the best of this good section 
will, by comparison, indicate what is required, close to the road to bo sur- 
faced. This natural mixture of sand and clay can be noticed where red 
clay and sand crop out, usually well up in the hills, having in ditches and 
cuts the appearance of red sandstone. A good stratum of well mixed 
sand and clay will stand perpendicular in cuts and ditches, resisting ero- 
sion almost as well as sandstone. A test of the best natural sand-clay 
mixtures will show the sand forms about 70 per cent of the whole. The 
test is very simple. Take an ordinary medicine glass, measure 2 ounces 
of the mixture into the glass and wash out the clay. Dry the remaining 
sand and measure again on the medicine glass. The loss will be the amount 
of clay originally contained in the mass. 

Before placing any sand-clay on the road, the road should be graded 
to the desired width. The surface of the graded road should bo flat or 
slightly convex. The sand-clay should be put on from 8 to 12 inches in 
thickness, depending on the character of the subgrade or foundation. 
With a hard clay for foundation, 8 inches of sand clay will suffice. If the 
subgrade is sand it is well to put on as much as 12 inches of the surfacing 
material. After a few hundred feet of surfacing material has been placed, 
a grading machine should be run over it to smooth and crown the road 
surface before the top becomes hard and resists the cutting of the blade. 
It is a good plan to turn the blade of the machine so as to trim the edges 
of the surface part, discharging the excess sand and clay onto the earth 
shoulders. After one round trip with the blade turned out, the remaining 
dress work with the machine should be with the blade turned in, with the 
exception of one trip down the center of road with the blade at right angles 
to the axis of the road for the purpose of distributing any excess of mate- 
rial left in the center. 

After the machine work, it is well to follow with a drag, which smooths 
any rough places left by the machine and leaves the road with a smooth, 
even surface. A sand-clay road, unlike other roads, cannot be finished 
in a short space of time. It can be left in an apparently finished condi- 
tion with a hard smooth surface, but it will be found on close examina- 
tion that the hard surface is in reality only a crust, below which there are 
several inches of loose material. After the first hard rain the crust soft- 
ens, the road becomes bad and the work appears to be a failure. This, 
however, is just what is needed to make it eventually good. After the 
surface has dried until the mass is in a plastic state, it should be dragged 
until the surface is once more smooth, with proper crown, and should be 
kept this way by dragging at least once a day until the sun has baked it 
hard and firm. The mistake of keeping traffic off during this process of 
resetting should not be made. The continuous tamping of the wheels of 
wagons and hoofs of horses is just what is needed to compact the sand- 
clay into a homogeneous mass. The ordinary roller is not very effective 
in this work, but corrugated rollers have given excellent results. One 
type which is widely used has 18 cast-iron wheels weighing 309 pounds 
each, which compress the bottom of the mixture first. As the material 
becomes more and moie compact the wheels ride higher and higher and 
finally the surface is so hard that the roller does not sink into it at all. A 
drag is an indispensable machine in the construd-ion of any kind of sand- 
clay road. 



50 AMEEICAN HIGHWAY ASSOCIATION 

2. Sand and clay placed on a soil foundation and mixed. This is nec- 
essary where the old road has neither a sand nor clay foundation and it 
is impossible to find the two ingredients ready mixed, but possible to get 
both in separate state near at hand. The clay should first be placed 
on the road to a depth of 4 inches and the required width. It is not 
wise to place more than a few hundred lineal feet of clay before the 
sand is hauled, as the clay rapidly hardens and makes the mixing process 
diflScult. After, say, 400 feet of clay has been placed, the clay should be 
broken by means of a plow and harrow, if it has become hard, and sand to 
a depth of 6 inches placed on it. This should be plowed and harrowed in 
thoroughly. This is best done immediately following a rain, as the two 
can be more satisfactorily mixed. The traffic aids the mixing and should 
be encouraged on the road. After the mass appears to be well mixed, the 
road should be properly shaped, as previously explained. The road should 
be given watchful attention and should sand or mud holes appear, a second 
plowing and mixing should be given it. 

3. Clay hauled on a sand foundation and mixed with the sand. The 
mixing process is similar to that described under second head. It is only 
necessary to add that as the foundation is sand, a little more clay will be 
necessary than where the foundation is of clay or soil. 

4. Sand hauled on a clay foundation and mixed with clay. The clay 
foundation should be plowed to a depth of 4 inches and harrowed with a 
disk or tooth harrow until the lumps are thoroughly broken or pulver- 
ized. Sand should then be added to a depth of 6 inches and mixed as be- 
fore described. 

Sand and clay can be mixed best when wet, but as most road construc- 
tion is done in the summer months, it is necessary to do most of the mix- 
ing dry and keep the road in shape after the first two or three rains, while 
the passing wagons and vehicles give the road a final wet mixing. A sand- 
clay road is the cheapest road to maintain, for the reason that it can be 
repaired with its own material. With a drag or grading machine ruts 
can be filled with material scraped from the edges, whereas on gravel or 
macadam roads, this is not possible. The repairing of these roads can be 
done almost exclusively with the drag, only enough hand work being re- 
quired to keep the gutters open and the growth of weeds cut on the should- 
ers. Holes are repaired by adding more sand-clay, and when many of them 
appear fresh sand-clay should be spread over the surface of the road. If 
the road gets into really bad condition, the roadbed should be plowed up, 
reshaped and fresh sand-clay added. This is unnecessary where the road 
is maintained properly and the travel is not too heavy for the type of 
construction. 



GRAVEL ROADS ^ 

At the close of 1914, 45 per cent, of the surfaced roads in the 
United States were gravel roads, as shown in detail in a table in 
Part III of this volume. The presence of good gravel in many 
parts of the countrj^ and the low cost of constructing and main- 
taining gravel roads will make them a leading type for many 
years to come. 

Some gravels are much better for road construction than 
others. In Michigan, where three-fifths of the surfaced roads 
are built of gravel, the value of this material for the purpose 
is held to vary with the percentage of pebbles in it, the road- 
building value of the rock of which the pebbles are composed, 
and the cementing properties of the fine material mixed with the 
pebbles. In this State at least 60 per cent by weight of the 
gravel for state reward roads must be pebbles larger than |-inch. 
No pebbles larger than 2J inches are used in the bottom of the 
road and none larger than IJ inches in the top. The binder 
required for holding the pebbles together is clay, uniformly mixed 
with the pebbles, free from lum.ps, and amounting to not over 
10 per cent of the total weight of the gravel. 

There is a large mileage of gravel roads in New Jersey, and 
as a result of experience with them, the State highway depart- 
ment rejects gravel with over 5 per cent retained on a Ij-inch 
circular opening and over 35 per cent retained on a ^-inch cir- 
cular opening. Three grades are recognized. Grade A is a 
pebble gravel with a clay binder with not less than 25 nor more 
than 35 per cent retained on a J-inch circular opening, not less 
than 40 nor more than 60 per cent retained on a 10-mesh sieve, 
not less than 8 nor more than 20 per cent passing a 200-mesh 
sieve, and the balance a fairly well graded sand. Grade B is a 
sandy gravel depending upon oxide of iron for its cementing 
properties, with 20 to 40 per cent retained on a 10-mesh sieve 
and 10 to 25 per cent passing a 200-mesh sieve. Of this material 
passing a 200-mesh sieve, at least 40 per cent must be soluble 
in a 1:3 dilution of hydrochloric acid. Grade C is gravel which 
does not fall under either of the previously mentioned grades but 
is approved by the engineer for the bottom part of gravel roads. 

^ Revised by Frederic E. Everett, State Highway Commissioner of New 
Hampshire. 

51 



52 AMERICAN HIGHWAY ASSOCIATION 

In Illinois, the State highway department requires the gravel 
to be rather uniformly graded in size from fine material to peb- 
bles that will just pass a 3|-inch ring, and not over 15 per cent 
of the mass (exclusive of clay) passing a J-inch ring. It must 
not contain over 5 per cent of loam but it must have 15 to 25 
per cent of clay by dry measure. If a local gravel does not form 
a good bond, the contractor must supply a bonding gravel for the 
top |-inch of the road. All of this material must pass a 1-inch 
screen and contain 40 per cent of pebbles retained on a i-inch 
screen and from 20 to 30 per cent of clay and loam, not more 
than 5 per cent being loam. 

The variations in these specifications show the range of prop- 
erties of the materials found useful by experience. Few attempts 
have been m.ade to prepare a general specification for road gravel 
on this account. The following requirements were adopted by the 
American Society of Municipal Improvements in 1916 and re- 
commended by the Committee on Materials for Road Con- 
struction of the American Society of Civil Engineers: 

Two mixtures of gravel, sand and clay shall be used, hereinafter desig- 
nated in these specifications as No. 1 product (for top course) and No. 2 
product (for middle and bottom courses.) 

No. 1 product shall consist of a mixture of gravel, sand and clay, with 
the proportions of the various sizes as follows: All to pass a 1^-inch screen 
and to nave at least 60 and not more than 75 per cent retained on a f-inch 
screen; at least 25 and not more than 75 per cent of the total coarse aggre- 
gate (material over ^-inch in size) to be retained on a f-inch screen; at 
least 65 and not more than 85 per cent of the total fine aggregate (mate- 
rial under J inch in size) to be retained on a 200-mesh sieve. 

No. 2 product shall consist of a mixture of gravel, sand and clay, with 
the proportions of the various sizes as follows : All to pass a 2^-inch screen 
and to have at least 60 and not more than 75 per cent retained on a J-inch 
screen; at least 25 and not more than 75 per cent of the total coarse aggre- 
gate to be retained on a 1-inch screen: at least 65 and not more than 85 
per cent of the total fine aggregate to be retained on a 200-mesh sieve. 

It is evident that the most useful information concerning the 
value of any gravel for road work is obtained by examining a 
road built of it. If there is a good gravel road and the source 
of this gravel is not known, a sample of the gravel can be analyzed 
mechanically by a portable sand tester, and the gravel deposits 
in the vicinity tested by the same instrument until one is found 
showing about the same properties. An exact agreement should 
not be expected. Tests of the gravel in a satisfactory road in 
the State of Washington and of the material in the pit from 
which it was obtained gave the following variations: 



GRAVEL ROADB 



53 



Mechanical Analyses of Identical Gravel Sampled at Pit and in the Road 



PASSING 


PIT 


ROAD 




per cent 


per cent 


200 sieve 


4.1 


6.4 


100 sieve 


8.0 


8.1 


80 sieve 


6.6 


4.7 


50 sieve 


16.3 


7.4 


40 sieve 


13.1 


6.9 



30 sieve 

20 sieve 

10 sieve 

8 sieve 

4 sieve 



PIT 


ROAD 


per cent 


per cent 


10.2 


6.5 


14.7 


12.1 


14.5 


12.7 


2.6 


3.4 


5.2 


9.5 



2 sieve 

J inch 

1 inch 

IJ inch 

l| inch 



PIT BOAD 



per cent 


per cent 


3.5 


8.3 


1.2 


5.7 




1.9 




6.4 



Where coarse gravel is composed of rock pebbles giving a 
cementitious powder some engineers consider it unwise to use 
enough clay binder to fill the voids. If roads of coarse gravel 
bound with a large amount of clay are used by many automobiles 
the pebbles become dislodged and the road does not become hard, 
it is claimed. Consequently these engineers prefer to use a 
smaller amount of clay and to allow the traffic to wear down the 
road and produce the necessary binder by attrition and internal 
disintegration of the mass of gravel. This process makes it neces- 
sarj' to maintain the road carefully for some time after its com- 
pletion, but is stated to give a better road eventually with some 
classes of gravel. 

In New England, where gravel roads have been built extensive- 
ly, it is generally considered safe to use on roads for light traffic 
the gravel from any pit where the face stands vertical and has 
to be loosened before it can be shoveled. Other gravels usually 
have to be supplied with a binder. It is always desirable to make 
a careful search for all deposits of gravel and an examination 
of the quality of each before deciding upon the deposit to use. 
In Dubuque County, Iowa, for instance several months were 
spent in such an investigation because the local limestone was 
too soft for road use. Finally a satisfactory pit was found Ij 
miles from the road to be improved, and by transporting it on 
a light narrow-gauge railway to the road and then distributing 
it by branches of this railway and by motor trucks and dump 
wagons, its cost on the road was kept down to a satisfactory 
figure. 

Preparing the Gravel 

The management of the gravel pit should receive enough study 
and attention to make sure that the material is delivered to the 
wagons or cars at the lowest cost. The organization for the 
purpose will depend upon the location of the pit, the quality of 
the gravel and the quantity of material to be taken out. Where 
there is only a small percentage of the gravel which is over size, 



54 AMERICAN HIGHWAY ASSOCIATION 

and the remainder runs a uniformly good mixture, the large 
stones can be removed by a flat gravel screen, or, on small works, 
can be forked out during loading. It is not always necessary to 
go to the expense of screening. With a good foreman in the pit 
it may be possible to get a proper mixture of the material from 
a pit where the gravel lies in strata of different sized pebbles, 
provided there is also a good foreman on the road, so that the 
strippings, if any, will be placed on the shoulders and the over- 
large m.aterial will be used for foundations in low places. 

Where there is a considerable proportion of overlarge stone 
in the gravel it is customary to set up a crushing and screening 
plant at the pit. For example, Kane County, Illinois, has an 
outfit consisting of a jaw crusher, screen, elevator and storage 
bin holding 15 cubic yards. The gravel is first screened, because 
by taking out the material of suitable size for road work only the 
large stone is fed to the crusher and its capacity is thereby much 
increased. The presence of the small stone in the crusher tends 
to clog it and retard the breaking of the large stone. The screened 
and crushed material is discharged by gravity from the bins into 
the 5-yard motor trucks which are used for delivering it. The 
pit material is delivered to the screen by a belt conveyor, 18 
inches wide and 40 feet long. One end of the belt is under a plat- 
form having a hopper over the belt. The gravel is brought by 
slip scrapers to the platform and dumped through the hopper 
onto the conveyor. 

In some plants of this character the gravel is run over a bar 
screen or^'grizzly" which holds back all oversize stone and delivers 
it to the crusher. This keeps the large stone entirely out of the 
screen. In Wisconsin work the screen has J-inch perforations 
for the first half of its length and Ij-inch perforations for the 
second half, giving three sizes of gravel. The jaws of the crusher 
are set to give about equal parts of the two coarser sizes separated 
by the screen. 

As the pebbles composing gravel are rounded and do not lock 
together as well as broken stone, it is customary to use somewhat 
smaller sizes of gravel than of crushed stone. Gravel obtained from 
beaches and rivers is usually more rounded than that from pits 
and consequently may not be so good for roads, unless suitable 
binding gravel can be used for a wearing surface or limestone 
screenings or other good binding material can be used with it. 

Pit-run Gravel Roads 

Many miles of gravel roads have been built by dumping the 
gravel on the roadbed, spreading it roughly and allowing 
traffic to consolidate it. The consolidation is a tedious process, 



GRAVEL ROADS 



55 



but good roads often result in the end, particularly if the road 
is kept well dragged so that ruts and holes are prevented. Bet- 
ter results are obtained, however, if the gravel is rolled after it 
is spread. The loads of large stone should be dumped at the low 
or soft places on the roadbed. In deep, mealy sand, the sub- 
grade is sometimes covered with marsh hay, wet sand or fine 

Cubic Yards of Loose Gravel Required to make One Mile of Road of Dif- 
ferent Widths and Thicknesses. Based on Table of Commissioner of Pub- 
lic Roads of New Jersey. 







THICKNESS OF ROAI 


) ATTKR CONSOLIDATION, 


INCHES 




WIDTH 


















6 


7 


8 


9 


10 


11 


12 


feet 
















6 


880 


1.027 


1,173 


1,320 


1,467 


1,613 


1,760 


7 


1,027 


1,198 


1,369 


1,540 


1,711 


1,882 


2,054 


8 


1,173 


1,369 


1,564 


1,760 


1,956 


2,151 


2,346 


9 


1,320 


1,540 


1,760 


1,980 


2,200 


2,420 


2,640 


10 


1,467 


1,711 


1,956 


2,200 


2,444 


2,689 


2,934 


11 


1,613 


1,882 


2,151 


2,420 


2,689 


2,958 


3,226 


12 


1,760 


2,053 


2,346 


2,640 


2,933 


3,227 


3,520 


13 


1,807 


2,224 


2,542 


2,860 


3,178 


3,496 


3,614 


14 


2,054 


2,396 


2,738 


3,080 


2,422 


3,764 


4,108 


15 


2,200 


2,567 


2,933 


3,300 


3,667 


4,033 


4.400 


16 


2,346 


2,738 


3,128 


3,520 


3,912 


4,302 


4,692 


17 


2,493 


2,909 


3,324 


3,740 


4,156 


4,571 


4,986 


18 


2,640 


3,080 


3,520 


3,960 


4,400 


4,840 


5,280 


19 


2,787 


3,250 


3,716 


4,180 


4,644 


5,109 


5,574 


20 


2,933 


3,422 


3,912 


4,400 


4,888 


5,378 


5,866 



Cubic Yards of Crushed Stone or Gravel Required to Give Different Depths 
when Lying Loose on One Mile of Roadways of Different Widths. Based 
on Table of Wisconsin Highway Commission. 









DEPTH OF LOOSE 


MATERIAL, 


INCHES 






WIUTU OF 


















BURS' ACE 




















1 


U 


U 


2 


3 


4 


5 


6 


feet 


cu. yds. 


cu. yds. 


CU. yds. 


cu. yds. 


CU. yds. 


CU. yds. 


cu yds. 


cu. yds. 


8 


130 


160 


195 


260 


391 


521 


652 


782 


9 


147 


180 


220 


294 


440 


587 


734 


880 


10 


163 


200 


244 


326 


489 


652 


816 


977 


12 


196 


240 


293 


392 


587 


783 


980 


1,171 


14 


218 


280 


342 


436 


684 


913 


1,141 


1,369 


15 


244 


300 


366 


488 


733 


979 


1,222 


1,466 


16 


261 


325 


391 


522 


782 


1,043 


1,304 


1,565 


18 


294 


367 


440 


588 


880 


1,174 


1,468 


1,760 


20 


326 


400 


488 


652 


978 


1,304 


1,632 


1,954 


22 


359 


440 


537 


718 


1,076 


1,434 


1,796 


2,148 


24 


392 


480 


584 


784 


1,174 


1,564 


1,960 


2,342 



56 



AMERICAN HIGHWAY ASSOCIATION 



Weight in Pounds Per Cubic Yard of Sand and Gravel. 
Resources of the United States, 1915." 



From "Mineral 







h3 






H 


STATE 




•< 
m 

2505 


> 

a 
o 

2790 


Alabama 


California 


2645 


2895 


Florida 


2605 


2680 


Illinois 


2820 


3005 


Indiana 


2700 


2945 


Iowa 


2720 
2580 


2850 
2830 


Kentucky 



Massachusetts 

Michigan 

Minnesota. . . . 

Missouri 

New Jersey. . . 
New York .... 
Ohio 



a 


> 
•< 

« 


2710 


2810 


2895 


2985 


2865 


2880 


2680 


2840 


2600 


2730 


2590 


2760 


2700 


2830 



Oregon 

Pennsylvania 

Texas 

Washington. . 
W. Virginia . . 
Wisconsin... . 
Average 



5 



2620 
2500 
2695 
2930 
2570 
2800 
2665 



2880 
2680 
2910 
3065 
2780 
2970 
2820 



Note: The average weights were obtained from 670 producers of sand 
and 560 producers of gravel in all parts of the country; the range was 
from 2200 to 4000 pounds for sand and from 2200 to 4200 pounds for gravel. 
The weights given for each state are the averages of the reports from ten 
or more producers in that State. 



brush to hold the gravel. The stone should be well raked and 
no stone larger than 2 inches should be allowed in the top of the 
road. 

It is best to lay the gravel in two courses, each 5 or 6 inches 
thick when loose. The spreading of the first course begins at the 
place on the road where the gravel reaches it and in this way 
the material is consolidated by the teaming over it. When this 
is very hard work enough clay is sometimes added to pack the 
gravel. Some engineers require this course to be harrowed. 
It is desirable to shape this course with a grading machine and 
roll it, but if the equipment is not available it can be improved 
by using a drag or a road plane, as described on page 266. 

After a considerable stretch of the bottom course has been 
finished, the second course can be started, beginning at the end 
farthest from the gravel pit, so as to have the teaming do as much 
consolidation work on the bottom course as possible. Some 
engineers require the entire bottom course to be finished before 
the second is started. It is best to harrow the second course be- 
cause pit-run gravel usually needs good mixing and the harrow 
will bring the large stones to the surface, so they can be thrown 
aside. If the gravel needs a binder the harrowing will help to 
distribute it evenly. If too much clay is added the road is likely 
to rut in wet weather and be dusty in dry weather. After the har- 
rovv^ing, the surface is shaped with a grader, if one is available, or 
with a drag or plane. It should then be rolled, and with some 
gravel the rolling gives the best results if the road is first wet. 

Gravel is a surfacing material, it will not make a defective 
roadbed good, although it may temporarily improve it. Con- 



GRAVEL ROADS 57 

sequently it is best to allow a new roadbed to be used as an earth 
road for a year, so it will have a chance to settle. If it is kept 
well dragged during this seasoning period, it will become hard 
enough to sustain the gravel. If it is known that gravel will be 
placed after a year's use, the earth road should be dragged to a 
very flat crown, in order to prevent too much crown in the gravel 
road. When gravel must be placed on a fresh roadbed, it is 
sometimes advisable to lay a 6-inch course and allow that to 
become consolidated by traffic before the second course is laid. 
If there are any defects in the roadbed they will become apparent 
during the earl}^ use of the road and can be repaired before the 
completion of the surfacing. If only the bottom course is laid 
the first season it should be well dragged, for inequalities in the 
bottom course are usually reproduced in the upper course, no 
matter how carefully the latter is laid and shaped. 

There are two methods of placing gravel. That usually em- 
ployed on pit-run gravel roads is called the feather-edge method. 
The roadbed to receive the gravel is graded to a very small crown 
and the gravel is spread on it to a nearly uniform thickness until 
within about 12 inches of the edge, when the bed is sloped off to 
a mere row of pebbles at the edge. In the second method of con- 
struction, a shallow trench, sometimes called a ''gravel bed" 
or a ''box," is excavated in the top of the roadbed, and the gravel 
deposited in it. If it rains this trench is likely to become muddy 
and to prevent this drainage channels should be cut through 
the shoulders to the side ditches. Bank gravel will become con- 
solidated and shed water more quickly than stream gravel and 
it is better suited for the trench method in consequvence. The 
feather-edge method is less expensive and more easily carried 
on if traffic must be permitted on the road during construction. 

The following explanation of the construction of a two-course 
feather-edge gravel road was written by H. E. Bilger, road engi- 
neer of the Illinois Highway Department: 

When the bonding material in the gravel is not entirely satisfactory 
with respect to both quality and quantity, it is usually advisable that 
two-course construction be adopted. Whether or not the vrork is to be 
done by contract, it is important that there be used some positive and 
accurate method of determining the volmne of gravel delivered upon the 
roadbed. There are several methods by which this can be accomplished, 
but experience seems to indicate that by the use of temporary side- 
board forms the desired results can be assured and this method is not 
uneconomical. 

Upon the satisfactory completion of the roadbed there should be set 
thereon, true to line and grade, temporary side forms having a width 
equal to the depth of the loose gravel, which should be shown on the plans. 
These boards should be held in place by stakes at such intervals as will 
prevent lateral deflection greater than about 3 inches from the true align- 
ment. Whether the gravel is hauled by wagons, motor trucks, industrial 



58 AMERICAN HIGHWAY ASSOCIATION 

railways, or other vehicles, it may be dumped directly upon the subgrade. 
After there has been placed upon the subgrade a sufficient quantity of 
gravel for the lower half of the road, it should be distributed to a uniform 
depth by the use of a blade grader, drag scraper, or otherwise. While 
this course is being spread, all the larger stone should be raked or other- 
wise placed directly in contact with the subgrade. Upon this course of 
gravel there should be placed such an amount of bonding clay as may be 
necessary in order that the gravel will comply with the specifications. 

After the gravel has been spread it should be thoroughly harrowed 
several times over until the cores formed by dumping it have been entire- 
ly loosened up to a density equal to that in the other portions of the gravel. 
The importance of this thorough harrowing can scarcely be overestimated, 
for in order to secure the results it is essential that the voids in the gravel 
be reduced to a minimum, which means that a maximum density of mate- 
rial must be obtained, and this density is closely approached by harrowing 
until the pebbles of the several sizes become so placed as to occupy the 
spaces between those of a large size. The cost of this harrowing as com- 
pared with the results obtained is practically negligible, and if necessary 
it would actually be more advisable to do away with the rolling and retain 
the harrowing than to do away with the harrowing and retain the rolling. 
The harrow should be of the stiff tooth type, and should have metal teeth 
at least 1-inch in diameter, extending about 6 inches below the frame. 
The spacing of the teeth should be such as will admit of the free passage 
of the stones between them, and yet so displace them as to produce the 
density desired. The design of the harrow should provide a weight of 
from 8 to 12 pounds upon each tooth. 

After the second course of gravel has been placed, it should be spread 
until its upper surface comes flush with the top of the side forms and its 
cross section conforms to that desired. The forms should then be removed 
and the gravel allowed to take its natural position. Upon this second 
course there should be distributed the necessary quantity of bonding 
clay. It should then be thoroughly harrowed several times, as before, 
until the cores formed by dumping the gravel have been entirely loosened 
up and the clay has been uniformly distributed throughout. The har- 
rowing should continue until a uniform density of material is obtained 
throughout the upper course. 

Having done this, the earth shoulders should be shaped by the nec- 
essary cutting and filling until the cross section conforms approximately 
to the finished work. Material other than the natural earth should not 
be used in forming these shoulders, and all vegetable matter should be 
strictly prohibited from entering into the work. Upon having shaped the 
shoulders, the graded roadway over the entire width should be rolled sev- 
eral times over until it is thoroughly compacted, forming a firm, smooth 
surface, free from waves and according to the requirement of the plans. 
The rolling should begin at the extreme outer edges of the shoulders and 
should work toward the center, at each rolling of the gravel allowing an 
overlap of one-half of the width of one of the rear wheels, and each wheel 
should cover the entire gravel surface. 

Should the condition of the gravel or its bonding material be such as 
not to compact readily under the action of the roller, sprinkling or other 
means should be employed to compact the gravel as the engineer may 
direct. The speed of the roller should not exceed about 100 feet per min- 
ute. It is quite probable that after rolling there will appear either on 
the shoulders or the gravel certain depressions and other irregularities. 
To correct these defects suitable material should be added or removed 
and they should then be rerolled. The finished surface should conform 
to the cross section shown on the plan and should preseni; a smooth and 



GRAVEL ROADS 59 

even appearance. Should the gravel, with its natural or artificial mixture 
of bonding cla}', for the upper 4 inches of the road, be of such character 
that it will not insure a satisfactory wearing surface with a dense body 
and uniform texture, a 1-inch coating of bonding gravel sh^ uld be applied 
uniformly over the entire surface of the gravel road. This bonding gravel 
should then be raked and rolled into the road surface until all the inter- 
stices are filled and the surface is smooth, of a uniform texture and free 
from waves. 

Screened Gravel Roads 

In some States, preference is given to gravel roads built like 
macadam roads, the gravel being screened so that the courses 
will be composed of material of different sizes. This is the case in 
Wisconsin, for instance. In that State, except on sandy road- 
beds, construction is started at the end of the road farthest from 
the gravel supply, when screened gravel is used, because the 
roller can be run continuously without interfering with the teams 
bringing the gravel. The first course consists of m.aterial from 
If to about 3 inches in size spread to a loose depth of 6 inches. 
The voids are filled with gravel under J-:nch in size and the road 
is then rolled. This course is laid for a distance of about 400 
feet, and the second course is then started. This consists of 
about 5 inches of ^ to l|-inch stone with the voids filled like 
those of the bottom course. The surface is shaped with a grader 
and rolled and flushed like a macadam road. 

In many instances better results are obtained, according to 
J. T. Donaghey, chief inspector of the Wisconsin highway com- 
mission, by crushing the gravel fine enough for practically all 
the material to pass a IJ-inch ring. The screen is partly jack- 
eted so that just enough of the material passing the J-inch open- 
ings is carried into the § to l|-inch size to fill the voids in the 
latter. This mixture is used in both the bottom and top courses 
and results in a type of road which Mr. Donaghey considers 
more easily built, more satisfactory and more cheaply maintained 
than any other gravel type. Where clay is added to assist in 
binding or there is naturally an excessive amount of clay in the 
gravel, it is advisable to place a covering of sharp sand or gravel 
on the finished surface to protect it until the excess clay has worked 
to the surface and washed off. 

In the work in Kane county, Illinois, to which reference has 
already been made, George N. Lamb, county superintendent of 
highways, places the lower course in a trench or box and rolls it 
and the shoulders until there is no difference of elevation where 
they meet. The second course is then placed with the edges 
feathering out a foot or two over the shoulders. 

The following instructions for preparing the subgrade were 
issued in 1914 by the Wisconsin highway commission: 



60 AMERICAN HIGHWAY ASSOCIATION 

Starting at the desired point, set two stakes opposite the reference 
stake, the distance between them being the width of the new road. To 
do this, refer to the grade sheet, which gives the distance from the side 
stake (placed when the survey was made) to the center of the new road. 
Subtract from this distance one-half the desired width of road and 
put in a stake with inside edge at this distance from the reference stake. 
Opposite this stake place another with its inside edge distant the width 
of the road from the inside edge of the first one. All stakes forsubgrade 
should be made of ^-inch round iron about 24 inches long, and about twenty- 
five should be kept on each surfacing job. Stake out 700 or 800 feet at a 
time. Be sure that the stakes are in line, except at bends or on curves. 
Usually curves will have to be staked out by eye to get good results. 

With a road plow cut as close to the inside edge of stakes as possible 
withour disturbing them, turning the furrow toward the center of sub- 
grade. Plow about 5 inches deep. One furrow on each side is generally 
suflBcient. Plow should be equipped with shoe or wheel and coulter. If 
a rooter is used, three furrows on each side will usually be necessary. Make 
first cut about 5 inches deep as close to stakes as possible, the next 6 inches 
nearer the center of the road. Drop the shoe down so rooter will run 
about 3 inches deep for the third cut, working 6 inches nearer center of 
subgrade than previous furrow. 

A light grader that can be handled with two horses is best for shaping. 
Use with the blade so set as to move the plowed ground from the center 
of trench or subgrade on to the bank outside of stake line. This work 
cannot be accomplished neatly with the grader alone, as some of the earth 
will roll back into the trench under the best of conditions. Make the 
trench deep enough. The depth at the sides should be at least the total 
loose depth of the two courses of material and more than this on sandy 
soils. It is much easier to throw out excess material with the road grader 
after the surface is laid than it is to bring extra material up from the 
ditches or to haul it in by wagons during the finishing when the trench has 
not been made deep enough to hold the stone. Nothing is more essential 
than a good solid shoulder, and the time to get it is before material is 
placed in the trench. In clay soils after making the trench, plow drains 
through the shoulders every 50 feet on both sides and every 25 feet at low 
points between hills and immediately clean them out so they will drain 
the subgrade in case of rain. 

The following procedure is not advised, as it is usually the most expen- 
sive way of getting shoulders. If the road has once been covered with 
crushed stone or gravel, and it is not desired to tear up the old surface, 
shoulders can be brought up to the stakes by bringing in dirt with the 
road machine from the side banks or from the ditches (if the latter mate- 
rial is fit to use), or can be hauled in with wagons. If the old road has a 
crown of one inch to the foot, it will take approximately 1,100 cubic yards 
of compacted material per mile to build up 6-inch shoulders and retain the 
minimum width of 20 feet on top. The cost of hauling and placing this 
material is usually very much greater than the value of the stone or gravel 
saved. As a matter of fact, no material is wasted if the subgrade or trench 
is cut in the old surface, the stone or gravel thrown out making an excel- 
lent shoulder. Failure is inevitable if an attempt is made to build a gravel 
or stone road with a heavy roller without first getting proper shoulders 
to support the material while it is being rolled. 

Straighten up stakes and drive them firmly. Tie a chalk or binder 
twine line to stakes on each side so line will draw on inside faces of stakes, 
drawing it tight. It is usually best to put in additional stakes at 50-foot 
points so this line will not sag. These lines a»e to guide the laborer in 
trimming the shoulders so the edges will be straight and the grade uni- 



GRAVEL ROADS 



61 



form. On a 9-foot road, if these lines are set 7 inches above center of 
flubgrade, they will be 1 foot higher than the bottom of trench at the 
shoulder. On a 15-foot road set lines 6 inches above center of eubgrade. 
They will then be one foot higher than the bottom of trench at the shoulder. 
The blade of an ordinary square point dirt shovel is 1 foot long and can be 
used by the laborer to tell when trench is deep enough at sides by setting 
blade of shovel up to line. When trench is finished, it should run with a 
uniform slope from center to edge. Clean out drainage trenches through 
shoulders, so that they really drain out from the trench. This will keep 
the trench from filling up in case it rains. It is well to widen the trencn 
and road on the inside of curves, and to elevate the outer edge of curves. 
After the subgrade has been properly shaped to the same crown (or, 
better, a slightly greater crown) than the finished road is to have, it should 
be rolled until hard, especially if recently filled. Any hollows that devel- 
op during the rolling should be filled. Roll enough, but stop before the 
top layer of earth starts to slip. Wet spots in the subgrade should be 
shoveled out, filled with good earth or cmders and rolled. Don't leave 
sink holes with the expectation of filling them with crushed stone. They 
must be dug out and refilled with good material if a firm surface is to ever 
be gotten at that point. 

In spreading gravel or broken stone many engineers place on 
the subgrade wood or concrete blocks of the desired loose depth 
of the course. In Wisconsin, however, the material is spread by 
requiring a load to cover a certain length and width of surface. 
The foreman is given a table of the length of 9-foot road which 
loads of different sizes will cover and the spreader is required to 

Length of Road in Linear Feet Which a Load of Stone of Given Size mil 
Cover to the Given Loose Depths. Based on Table of Wisconsin Highway 
Commission. 



WIDTH 


LOOSE 
DEPTH 


SIZE OF LOAD IN CUBIC TABDS 


or ROAD 


1 


U 


U 


li 


2 


2} 


2J 


2i 


8 


feet 


inche* 


feet 


feet 


f«et 


feet 


feet 


feet 


feet 


feet 


feet 


8 


3 

4 
5 
6 


13.5 
10.1 
8.1 
6.75 


16.9 

12.6 
10.1 

8.4 


20.2 
15.2 
12.1 
10.1 


23.6 
17.7 
14.1 
11.8 


27.0 
20.2 
16.2 
13.5 


30.4 
22.6 
18.2 
15.2 


33.7 
25.3 
20.2 
16.9 


37.1 

27.8 
22.3 
18.5 


40.5 

30.3 
24.3 
20.3 


9 


3 
4 
5 
6 


12 
9 

7.2 
6 


15 
11.25 

9 

7.5 


18 

13.5 

10.8 

9 


21 

15.75 
12.6 
10.5 


24 
18 

14.4 
12 


27 

20.25 
16.2 
13.5 


30 
22.5 

18 
15 


33 

24.75 

19.8 

16.5 


36 
27 

21.6. 
18 


10 


3 
4 
5 
6 


10.8 
8.1 
6.5 
5.4 


13.5 

10.1 

8.1 

6.7 


16.2 

12.2 

9.7 

8.1 


18.9 

14.2 

11.3 

9.4 


21.6 
16.2 
13.0 
10.8 


24.3 
18.2 
14.6 
12.1 


27 

20.2 
16.2 
13.5 


29.7 
22.3 
17.8 
14.8 


32.4 
24.2 
19.4 
16.2 


12 


3 
4 

5 
6 


9 

6.7 
5.4 
4.5 


11.2 

8.4 
6.7 
5.6 


13.5 

10.1 

8.1 

6.7 


15.8 

11.8 

9.4 

7.8 


18.0 

13.5 

10.6 

9 


20.2 
15.1 
12.1 
10.1 


22.5 
16.9 
13.5 
11.2 


24.7 
18.5 
14.8 
12.3 


27.0 

20.2 
16.2 
13.5 



62 AMERICAN HIGHWAY ASSOCIATION 

make the loads cover just this length. When this method is 
followed it is convenient to have the loads hauled of the same 
size. The man placed in charge of the spreading should be se- 
lected carefully, because a large amount of money can be wasted 
by placing too much material on the road. The depth of the 
loose material should be checked as often as possible on this 
account. 

When the gravel is bought by weight it is the Wisconsin rule 
to take the weight of a cubic yard of pit gravel at 3000 pounds 
and of crushed gravel at 2650 pounds. If the material is wet 
it will weigh more than when it is in a normal condition and al- 
lowance should be made for this. 

Special Binders 

Gravel roads are now being built for quite heavy traffic with 
binders giving greater toughness to the road than clay or rock 
powder will afford. Examination of many roads after several 
years of use has shown that there is less large stone and more 
small stone in them than when they were built. This change 
is considered due to the internal disintegration of the stone by 
the loads coming upon it, part of the reduction taking place when 
the road is heavily rolled during construction and part later under 
heavy travel. The special binders are used to hold the stone so 
firmly together that after the rolling of the road there will be no 
further internal disintegration. The method of using bituminous 
binders for this purpose is explained in the chapter on bitumi- 
nous roads, and the method of using glutrin in the chapter on 
broken stone roads. 

Maintenance 

The maintenance of gravel roads must begin immediately 
after the road is thrown open to travel. A small hole in a gravel 
road, unless immediately repaired, soon becomes a large hole. A 
few large holes mean a ruined road and a large expense for resur- 
facing. Furthermore a gravel road, no matter how well rolled, 
cannot be considered finished until traffic has gone over it and 
tested every part. For this reason, some engineers allow traffic 
on the road before the roller has left it, so that any weak places 
may be revealed and repaired at once while the equipm^ent is 
still at hand. The rounded pebbles of pit gravel do not inter- 
lock like pieces of crushed stone but are usually held together 
by a clay binder which is not so strong as the cementitious pow- 
der from some classes of rock. Until travel has broken down 
the pebbles and furnished rock powder which will act with the 
clay and form a rigid mass, a gravel road is not so firm as a crushed 
stone road and needs more maintenance. 



GRAVEL ROADS 63 

The gravel roads of New Hampshire are used throughout the 
summer by a heavy automobile traffic, particularly on Satur- 
days and Sundays. They are nevertheless kept in good condition 
by the patrol system of maintenance at very low cost, consider- 
ing the destructive use to which they are subject. Each patrol- 
man has a section for which he is responsible, and a number of 
sections are united in a division under the general supervision 
of a maintenance foreman, who is in immediate charge of all main- 
tenance work and reports to the division engineer. Each patrol- 
man must supply a horse and dump cart, shovel, pick, hoe, 
rake, stone-hook, axe, iron bar, iron chain and tamp. Special 
tools are furnished by the State highway department. The meth- 
ods of maintainance are indicated in the following quotations 
from the instructions issued to the patrolmen: 

One dragging in the spring is worth two in the summer. It is better 
to drag a mile of road several times and get it in good condition, than to 
drag 2 or 3 miles and not finish any part of it. Don't drag a soft section 
when it is so wet that the first vehicle to pass will rut it all up. First 
fill the holes and ruts with new material and then drag as the surface dries 
out. Every patrolman should have material dumped in small piles along 
the side of his section so that on a rainy day he can at once fill all holes 
and ruts in which water is collecting. 

When the weather is unsuitable for dragging, as during a dry spell, all 
patrolmen should cart on all the new material possible in order to fill all 
ruts and holes and resurface worn-sections. Carting is very essential 
during dry periods and should never be neglected. Whenever a patrolman 
is in doubt as to what to do next the general rule is to cart new material, 
for all roads are wearing out under travel and it is necessary that the 
surface be continually renewed to take the place of the old material that 
is thrown out as mud or blown away as dust. 

Save all the sods, leaves, rubbish, stones and refuse that you clean off 
your road and dump this waste material in places where the bank is steep 
so that by flattening the side slope there will be no need of a guard-rail, 
or dump the material back of a present guard-rail so that later this guard- 
rail can be removed. 

Oiling gravel roads generally requires careful preparation of 
the surface because the large amount of clay binder has a ten- 
dency to interfere with the formation of a satisfactory oiled 
surface. Consequently the surface should be thoroughly cleaned 
and a comparatively light oil used. The first applications are 
likely to be disappointing, but if holes and ruts are filled promptly, 
two or three applications on carefully cleaned surfaces during 
the first year will eventually give a good wearing surface, pro- 
vided the roadbed and gravel have been thoroughly consolidated 
and the traffic is not too heavy for this type of road. It is the 
general opinion at present that surface applications should not 
be made until a gravel road has had at least one year's service. 
The methods of doing the work are given in a later chapter. 



WATER- BOUND MACADAM ROADS 

Water-bound macadam roads are adapted to highways carry- 
ing moderate traffic, for experience shows that even when a large 
part of the traffic is motor-driven this type of construction can 
be maintained successfully by surface applications, as described 
in a later chapter. Where a gravel road is not quite able to carry 
the traffic, a macadam top course on a gravel base has been 
adopted as a standard type by the highway departments of a 
number of States. The following statements give the views 
regarding water-bound macadam held by three State highway 
departments having a large mileage of it under their charge: 

New York: The department is still building a large mileage of water- 
bound macadam. Because of the presence of local material and other fa- 
vorable conditions this is, in cost, the cheapest durable road which can be 
built; and it is the belief of the department that on all roads of ordinary 
or light traffic this type is still a satisfactory one for general use. Of 
course this type must have surface treatment with oil, and this is planned 
for in all cases. (Edwin Duffey, State commissioner of highways, 1916.) 
Michigan: During the early existence of the department, macadam 
roads constituted as much as 50 per cent of the mileage constructed. As 
the use of the automobile became more widespread, the percentage of 
macadam roads built each year decreased, owing to the excessive cost of 
maintaining this type under the automobile traffic. Within the past two 
years, however, waterbound macadam roads have been again growing in 
favor, because it has been found possible with a bituminous surface treat- 
ment to maintain them in a condition comparable in the point of service 
to the higher types of roads. The first treatment, which is made after 
the road has been seasoned by opening it to traffic for three or four months, 
is essentially a part of the initial cost of construction. (Frank F. Rogers, 
State highway commissioner, 1916.) 

Wiscom^in: It is not at all an economical type of surfacing unless in- 
tensely maintained with surface treatments and a patrol system, but when 
so maintained gives economical service even on heavily traveled roads. 
(Wisconsin highway commission, 1916.) 

Stone 

The roadbuilding properties of different rocks are explained in 
the next chapter. The following notes on the selection of stone 
were prepared by Prevost Hubbard and Frank H. Jackson, Jr.^ 
The ideal rock for the construction of a water-bound macadam 

1 "The Results of Physical Tests of Road-building Rock," Bulletin 370, 
United States Department of Agriculture. 

64 



WATER-BOUND MACADAM ROADS 



65 



road resists the wear of traffic to which it is subjected to just 
that extent which will supply a sufficient amount of cementitious 
rock dust to bind or hold the larger fragments in place. It is 
generally admitted that the ordinary macadam road is not well 
suited to any considerable amount of automobile traffic, because 
such traffic rapidly removes the binder without producing fresh 
material to take its place. 

Cementing value is a necessary quality for rocks used in mac- 
adam road construction. As determined by test, cementing 
values below 25 are called low; from 26 to 75, average, and above 
75, high. In general, the cementing value should run above 25. 
For rocks which show a low French coefficient of wear, however, 
a relatively high cementing value is more necessary than for 
those which have a high French coefficient. Interpretation of 
results of the cementing value test is subject to a number of 
influencing considerations. For instance, it has been found that 
certain feldspathic varieties of sandstone give excellent results 
in this test, while experience has shown that they do not bind 
well when used in the wearing course of macadam roads. In 
the case also of certain varieties of the trap group, low results 
are frequently shown by laboratory tests for rocks which bind 
quite satisfactorily upon the road, provided traffic is sufficiently 
heavy to supply the requisite amount of fine material. Certain 
granites, gneisses, and schists which are not suitable for use as 
binding material give good results in this test. In such cases 
it is usually found that the highly altered nature of the material 
reduces its toughness and resistance to wear to such an extent 
as to condemn it for use. 

Experience has shown that in general the following table of 
limiting values for the French coefficient of wear, toughness, and 
hardness may be used in determining the suitability of a rock 
for the construction of the wearing course of a macadam road: 

Limiting Values of Physical Tests of Rock Suitable for Water-hound 

Macadam 



Light 

Moderate 
Heavy 



FRENCH 
COEFFICIENT 



5 to 8 
9 to 15 
16 or over 



PERCENTAGE 
OF WEAR 



5 to 8 
2.7 to 5 
Under 2.7 



TOUGHNESS 



5 to 9 
10 to 18 
19 or over 



HARDNESa 



10 to 17 
14 or over 
17 or over 



With relation to the limitations for hardness it may be noted 
that when any given value for toughness falls within certain 
limits which define the suitability of the material for macadam 
road construction under given traffic conditions, the corre- 



66 AMERICAN HIGHWAY ASSOCIATION 

spending value for hardness will fall within similar limits for hard- 
ness. In this connection it will be seen in the table that a max- 
imum, limit for hardness is only given in the case of light traffic. 
It has been found that the great majority of samples having a 
French coefficient of wear of from 5 to 8 and a hardness of over 
17 are granites, quartzites, and hard sandstones, which are unsuited 
for use in the wearing course of water-bound macadam roads 
due to their lack of binding power. 

The weight of a cubic yard of crushed stone varies consider- 
ably, depending upon the rock, the size to which it is broken 
and the amount of shaking the sample receives before its volume 
is measured. The range in weight of a cubic foot of solid rock 
is 162 to 221 pounds for trap, 165 to 200 pounds for schist, 156 
to 175 pounds for felsite, 156 to 193 pounds for quartzite, 125 
to 193 pounds for limestone, and 125 to 187 pounds for granite. 
The total range from the lightest limestone to the heaviest trap 
is over 75 per cent and the crushed rock will show the same varia- 
tions. Consequently, when broken stone is bought by weight 
it should be actually weighed before estimating the quantity re- 
quired for good work. 

Crushed stone is the most important branch of the stone in- 
dustry. The production of this material for road building in 
the different states is given in a table on page 198 of this book. 
The requirements for railroad ballast and concrete as well as for 
road work are so large that commercial broken stone is avail- 
able in many parts of the country at a lower price than the cost 
of quarrying and crushing local material. It is sometimes eco- 
nomical, even at a greater initial cost, to import stone from a 
distance if thereby a more durable road may be had than is pos- 
sible with the use of local stone. 

Much of the stone is crushed locally, usually in portable plants. 
These comprise a crusher with an engine and boiler, revolving 
screens, portable bins and an elevator to lift the stone after it 
is crushed into the screen and sometimes into the bins. The 
capacity of a crusher should be adjusted to the road roller ca- 
pacity. If the crusher furnishes more stone than the roller can 
consolidate, it is too large to work economically. If the crusher 
can not supply enough stone to keep the roller at work, the lat- 
ter will operate uneconomically. Furthermore the arrangements 
for supplying stone from the crusher to the road must be such 
that the expensive equipment at each end of the line will be 
kept operating all the time. There is some difference of opin- 
ion as to the proper capacity of a crusher, for in some sections 
of the country it is held that from 60 to 80 cubic yards of 
broken stone is as much as a single roller will consolidate properly, 
while in other sections it is held that a roller which does not con- 
solidate 75 tons per day is not doing good service. 



WATER-BOUND MACADAM ROADS 67 

Where the stone supply is limited to ledges at infrequent inter- 
vals but little choice in the location of the crushing outfit is pos- 
sible. If field stone or ledges are available alongside the road 
at frequent intervals a crusher can serve about two miles of 
road most economically. Local conditions, however, affect the 
proper arrangement of the plant so greatly that no precise rules 
can be drawn up. It occasionally happens that the availability 
of water for the boiler is of more importance than any other 
factor in determining the location of the outfit. 

If possible, the crusher should be set low enough so that a plat- 
form can be built at the level of the opening into which the stone 
is dumped. The carts are driven onto this platform and the ma- 
terial is handled most economically in this manner. The men who 
set up the plant should have had experience in this work. Much 
depends on the proper alignment of the several parts and the 
delays in operation will be avoided if the work is done properly 
in the first instance. 

The screens in such portable plants have three sections about 
4 feet long and 30 inches in diameter. The first section has per- 
forations which are |-inch in diameter. The perforations of the 
second section are generally IJ inches in diameter where com- 
paratively hard stone is used and Ij inches in diameter where 
softer stone is employed. With the very soft stone used in some 
of the Central States, the perforations are sometimes 2| inches, 
and the third section of the screen is omitted. The perforations 
in the third section are from 2 to 2J inches in diameter as a rule, 
depending upon the maximum size of the stone which is allowed 
in the road, but this maximum size varies widely in different 
States. In New York stone up to 3i inches in size is used in the 
bottom course and in Ohio pieces of sandstone as large as 6 inches 
in their longest dimensions are permitted in the bottom course 
of some roads. Stone passing a 4-inch circular opening is also 
permitted under some conditions. In Wisconsin the bottom 
course is usually made of stone 2 to 3 J inches in size; in this case 
the perforations in the screen are ^, 2 and 3J inches. 

The stones too large to pass through the openings in the third 
section of the screen drop out and are run through the crusher 
again. There is sometimes a conveyor to carry these tailings 
from the end of the screen to the crusher. The jaws of the crusher 
should be set to give as few tailings as possible and the length 
of the screen sections should be adjusted to accomplish the same 
purpose. The operation of the screens should be observed from 
time to time in order to make sure that material which should 
pass the openings in each section does not flow along the screen 
so rapidly that there is a failure to separate it out by the right 
section of the screen. If the screen revolves too rapidly fine 



68 AMERICAN HIGHWAY ASSOCIATION 

material will be carried into the coarser grades. Stone purchased 
from commercial crusher plants is often observed to run small^ 
the best separation occurring in the product which is obtained 
during a time of minimum demand. This is because more time 
is then given to the stone in its passage through the screens. 
It is impracticable to obtain a complete gradation of the sizes 
of stone and for this reason highway engineers often permit vari- 
ations from the nominal maximum and minimum dimensions 
of any size. For instance the J-inch stone specified in New 
Jersey may contain up to 5 per cent of material larger than 1} inch 
and up to 8 per cent smaller than f inch, although the nom- 
inal range of size is from f to 1} inch. 

There is no uniformity in the designation of the sizes of crushed 
stone; what is termed as No. 1 stone in Ohio is entirely different 
from No. 1 stone in New York. 

Drainage 

The investment in a macadam road is so great that every pre- 
caution should be taken to have the roadbed thoroughly drained. 
The methods of doing this were explained in the chapter on 
drainage. If they are not employed wherever necessary the road 
will inevitably become rutted and marked by holes during pro- 
longed wet weather, and the maintenance of such places will 
entail an annual expenditure far greater in the end than the cost 
of proper drainage work. 

Formerly Telford foundations were used in all wet, soggy 
ground under well-built broken stone roads but experience has 
shown that with good underdrainage equally satisfactory foun- 
dations can be built of coarse gravel. This is dumped on the 
bottom of the road after the soft material has been excavated 
to a considerable depth. The mass of gravel should be drained 
into the side ditches by constructing blind drains through the 
shoulders at intervals of not over 50 feet. 

Where suitable field stone is available for a Telford foundation 
it is still sometimes used. The New York requirements for 
stone for this purpose are a thickness of not less than 1§ inches, 
a depth equal to the depth required for the foundation, from 6 
to 8 inches, and a length not more than one and a half times 
the depth. The New Jersey specifications require stone 5 to 
10 inches long, 2 to 4 inches wide and at least 6 inches deep. 
Some engineers advise placing this stone on a bed of gravel, while 
others believe that if gravel is available it is best to make the 
entire base of it and not employ Telford, since the latter is quite 
expensive. The stone must be set on their broader base, length- 
wise across the road, and wedged by driving small stone into 



WATER-BOUND MACADAM ROADS 69 

the interstices. The projecting points should be broken off 
with a stone hammer, the depressions in the top filled with stone 
chips, and the foundation rolled. 

The V-shaped drain described on page 27 is a substitute for 
a Telford foundation which has received much favor in some 
states. 

Sub-Grade 

It is necessary to place the stone for a macadam road in a box 
or trench in order to roll it successfully. The method of exca- 
vating the sub-grade was described on page 60. The bot- 
tom must be slightly crowned. This is for two reasons; first to 
shed any water which may sink through the macadam, and 
second, to keep the amount of stone required for the road to the 
minimum actually necessary. The sub-grade must be rolled 
until hard in order, first, that the stone placed on it can not be 
driven into it and thus serve no useful purpose, and second, to 
turn toward the sides of the road, into the blind drains leading 
to the ditches, any water which may penetrate the courses of 
stone. 

The depth of the box or trench is fixed by the desired 
depth of the macadam roadway. This is rarely less than 6 
inches at the center and is sometimes considerably more, al- 
though there is a question whether a greater thickness than 8 
inches after rolling serves any useful purpose. The harder and 
tougher the stone, the less need be the thickness of the road, 
provided the sub-grade is firm. Usually the sides of the macadam 
roadway are 1 to 2 inches thinner than the center. 

On very sandy soils, to keep the sand from working up through 
the stone, a covering of clay, hay, straw, or fine brush is spread 
over the subgrade. 

Placing the Broken Stone 

It is customary to begin placing the broken stone as soon as 
a few hundred feet of the subgrade has been prepared to receive 
it, because it is undesirable to expose the rolled earth surface to 
the danger of drenching by rains for a longer period than is 
necessary. 

The first course is rarely if ever spread to a greater depth than 
6 inches when loose, because a roller cannot compact a deeper 
course of stone in a satisfactory manner. The thickness is sel- 
dom less than 4 inches. The largest size of the screened stone 
is used. In some states it is forbidden to dump the stone di- 
rectly on the subgrade, on the ground that this leaves a mass of 
consolidated small stone in the center of the heap which remains 



70 



AMERICAN HIGHWAY ASSOCIATION 



almost intact when the pile is leveled. Accordingly the stone 
must be deposited on dumping boards about 6 feet long and 3 
feet wide, from which it is shoveled to the subgrade. This is no 
longer a generally adopted requirement, however, but it is not 
unusual to require a load to be deposited in several dumps 
so that the least amount of shoveling and raking will be required. 

Costs Per Mile Corresponding to Different Costs Per Square Yard. Based on 
Table Published by Commissioner of Public Roads of New Jersey 

20 



11,7331 



Width, feet 


8 


10 


12 


14 


16 


18 


Square 
yards, 
per mile 














4,693J 


5,8661 


7,040 


8,213i 


9,3861 


10,560 


Cost per sq. 














$0.25 
0.30 
0.35 
0.40 
0.45 


$1,173.33 
1,408.00 
1,642.67 
1,877.33 
2,112.00 


$1,466.67 
1,760.00 
2,053.33 
2,346.67 
2,640.00 


$1,760.00 
2,112.00 
2,464.00 
2,816.00 
3,168.00 


$2,053.33 
2,464.00 
2,874.67 
3,285.33 
3,696.00 


$2,346.67 
2,816.00 
3,285.33 
3,754.67 
4,224.00 


$2,640.00 
3,168.00 
3,696.00 
4,224.00 
4,752.00 


0.50 
0.55 
0.60 
0.65 
0.70 


2,346.67 
2,581.33 
2,816.00 
3,050.67 
3,285.33 


2,933.33 
3,226.67 
3,520.00 
3,813.33 
4,106.67 


3,520.00 
3,872.00 
4,224.00 
4,576.00 
4,928.00 


4,106.67 
4,517.33 
4,928.00 
5,338.64 
5,749.33 


4,693.33 
5,162.67 
5,632.00 
6,101.33 
6,570.67 


5,280.00 
5,808.00 
6,336.00 
6,864.00 
7,392.00 


0.75 
0.80 
0.85 
0.90 
0.95 


3,520.00 
3,754.67 
3,989.33 
4,224.00 
4,458.67 


4,400.00 
4,693.33 
4,986.69 
5,280.00 
5,573.33 


5,280.00 
5,632.00 
5,984.00 
6,336.00 
6,688.00 


6,160.00 
6,570.67 
6,981.33 
7,392.00 
7,802.67 


7,040.00 
7,509.33 
7,978.67 
8,448.00 
8,917.33 


7,920.00 
8,448.00 
8,976.00 
9,504.00 
10,032.00 


1.00 
1.05 
1.10 
1.15 
1.20 


4,693.33 
4,928.00 
5,162.67 
5,397.33 
5,632.00 


5,866.67 
6,160.00 
6,453.33 
6,746.67 
7,040.00 


7,040.00 
7,392.00 
7,744.00 
8,096.00 
8,448.00 


8,213.33 
8,624.00 
9,034.67 
9,445.33 
9,856.00 


9,386.67 

9,856.00 

10,325.33 

10,794.67 

11,264.00 


10,560.00 
11,088.00 
11,616.00 
12,144.00 
12,672.00 



$2,933.33 
3,520.00 
4,106.67 
4,693.33 
5,280.00 

5,866.67 
6,453.33 
7,040.00 
7,626.67 
8,213.33 

8,800.00 

9,386.67 

9,973.33 

10,560.00 

11,146.67 

11,733.33 
12,320.00 
12,906.67 
13,493.33 
14,080.00 



Note: When the cost per square yard is greater than $1.20, the corre- 
sponding cost per mile can be found by adding to the tabulated cost for a rate 
of $1.00 per square yard, the tabulated cost for a rate equal to the difference 
between the given rate and $1.00. The costs per square mile for widths 
greater than 20 feet are found by adding together the costs for two of the 
tabulated widths which will give the desired width. 

The easiest method of distributing the stone is by using an auto- 
matic spreader wagon which deposits it in a layer of approxi- 
mately the right thickness. The methods of determining the 
thickness are explained on page 61. 

When a hundred feet or so of the first course has been spread, 
the rolling should begin. A roller weighing about 600 pounds 



WATER-BOUND MACADAM ROADS 71 

per inch of width of roll is usually recommended for rolling; hard 
rock, but one of three-fourths this weight will probably do bet- 
ter work with soft limestone. The roller starts at the edges of 
the stone and care should be taken that the shoulders are not 
crushed during the trips near the sides of the trench. The roller 
should not be run much faster than 100 feet per minute. After 
both sides are moderately firm, the roller should move gradually 
toward the center until the whole lower course is thoroughly 
compacted. The rolling should be stopped as soon as the 
pieces of stone begin to break. Sometimes it is found that 
a wavy motion continues and the stone will not compact. 
This may be due to a wet subgrade, which will probably give 
no trouble if allowed to dry for a day or two, or it may be due 
to the use of a very hard stone, when the application of a little 
sand or fine gravel may remedy the difficulty. With some 
soft, coarse, gravel stones a crawling motion may be noticed, 
which can be prevented by a light sprinkling of coarse sand, 
stone screenings and sometimes by water. The rolling is con- 
tinued until the stone has no movement when the men walk over 
it. If depressions develop during the rolling they must be 
filled with stone of the same size as that used in the course 
and rolled until firm. 

Some engineers advise harrowing the loose stone with a spike- 
tooth harrow in order to mix the stone thoroughly and to save 
a part of the rolling. This would be of advantage if full loads of 
stone were dumped directly on the subgrade, for it would break 
up the cores of small stone in the center of the piles. Other 
engineers recommend using a blade grader to shape the loose 
stone just before rolling. 

It is not customary to apply a binder of gravel or screenings 
to the bottom course in some states and it is required in others. 
It is apparently a detail depending considerably upon the hard- 
ness of the stone used. If the stone is relatively soft and the 
bottom course is constructed of a large size of stone, a binder 
may prevent the internal disintegration of the stone under loads 
to some extent, but with the somewhat smaller, hard trap rock 
used in Massachusetts, for instance, screenings are unnecessary. 

After about a hundred feet of the bottom course has been 
rolled, the second course is spread. This consists of the size from 
J to IJ or 1^ inches, and the loose depth is 3 to 5 inches. Large 
loads should not be dumped directly on the bottom course. The 
top course is usually given its final shaping with rakes. This 
course is rolled commencing on each outer edge with the rear 
wheel half on the stone and half on the shoulders; the roller is 
gradually worked toward the center. If depressions are devel- 
oped during this work, they must be filled, and the rolling should 
continue until the surface is hard and uniform in contour. 



72 AMERICAN HIGHWAY ASSOCIATION 

The surface is then covered with the binder. The material 
used for this purpose varies with the character of the stone in 
the top course. Generally screenings are employed, but in states 
where the top course is composed of rather large sizes of stone 
the screenings have small stone mixed with them. In Mary- 
land limestone screenings are not permitted with trap rock with- 
out the consent of the engineer. A. R. Hirst, State highway engi- 
neer of Wisconsin, advises using a clayey pea gravel or disinte- 
grated granite with crushed quartzite or granite, and if these 
are unavailable he prefers a bituminous binder. 

Screenings are rarely if ever permitted to be dumped on the 
road. They should be placed in piles along the road at such 
intervals that they can be distributed readily and enough mate- 
rial will always be available. In Massachusetts it is not cus- 
tomary to place the screenings to a greater depth than 1 inch. 
In Michigan the depth is about f inch and in Wisconsin about 
J inch on State roads. 

Although the screenings are sometimes rolled dry, after being 
spread, the usual practice is to sprinkle the road with water 
before rolling. The road must be sprinkled until the screenings 
are thoroughly wet and do not stick to the wheels of the roller. 
Where hard, small stone is used in the top course more water 
is generally employed than where the stone is larger, and an 
attempt is made to flush the screenings into the interstices be- 
tween the stones. If the screenings are picked up by the roller 
at any time, more water must be applied. The sprinkling and 
rolling are continued until water is carried along in front of the 
roller wheels at every point of the road. 

Rolling must be done carefully for the appearance of the road 
will depend upon this work. 

After the road has dried sufficiently, the shoulders should 
be smoothed off with a road machine, if one is available. The 
shoulders should be trim^med so the water can flow from the 
center of the road to the ditches along every foot of the way. 
All surplus material should be rem.oved, and the shoulders should 
be rolled as far out as it is safe to run the roller. 

Glutrin Binder 

For a number of years, glutrin has been used extensively as 
a binding material for both gravel and broken stone roads. It 
is an adhesive binding liquid whose base is the lignin derived 
from the sulphite pulp wood process. It is sold in a concentrated 
state and should be diluted with water before use. 

It should be understood that when the road material to be 
treated is other than stone, it should contain at least 10 per cent 



WATER-BOUND MACADAM ROADS 73 

of clay. When this is lacking in the original road material, it 
should be evenly added as the road material is put in place. 
When used on gravel or sand-clay roads, glutrin should be di- 
luted with water in the proportion of one part glutrin to not 
less than three parts water. This mixture should be applied 
by means of any distributor which will spread it uniformly. 
The application should be continuous, so that the road is kept 
moist, but not so rapidly as to permit the forming of pools or 
the flowing off to the sides. Penetration must be secured, and 
consequently the distributor should make at least four trips 
over the road in applying the amount of glutrin called for in the 
specifications. This is usually about J gallon of glutrin to the 
square yard. 

When used in the construction of broken stone or slag roads, 
the glutrin should be applied during the process of puddling 
the top course. The puddle should be begun as usual with plain 
water, but as soon as the screenings are thoroughly saturated, 
glutrin should be placed in the sprinkler in the proportion of one 
part glutrin to five parts water, and the puddling completed 
with this mixture. The specifications usually call for ^ gallon 
of glutrin to the square yard to be used in this process. A still 
stronger bond can be secured if, after the road has been pud- 
dled in this manner, it is allowed to dry out and a surface ap- 
plication is then made over the center 80 per cent of the width 
of the road, of 0.2 gallon of glutrin, diluted in the proportion of 
one part glutrin to three parts water. As soon as the road is 
dry, it can be opened to traflic. 

There have been many miles of glutrin-bound roads con- 
structed in Connecticut and New York, which have been given 
a bituminous top course, or even an oil treatment, the purpose 
being to bind the mass of stones thoroughly together with glu- 
trin to prevent the internal disintegration of the gravel or stone 
by traffic and to protect the glutrin from surface water. 

Glutrin should not be used with a pure siliceous material like 
quartz, unless at least 10 per cent of clay is added. With broken 
stone, the fine material produced in rolling, furnishes a substi- 
tute for the clay required with gravel. 

Maintenaiice 

Where there is very little automobile traffic the old-fashioned 
methods of maintenance are still applicable. If the road was 
built late in the fall, particularly if trap rock was used, it is pos- 
sible that loose stone will appear on the surface in the spring. 
They should be removed and need cause no apprehension. Holes 
and ruts should be filled with small stone and screenings, prefer- 



74 AMERICAN HIGHWAY ASSOCIATION 

ably during a rain so the traffic will begin to bind the patch as 
soon as the weather clears. When the top course has been worn 
down so that the large stone of the bottom course show in places, 
the road should be repaired. If the top course is to be less than 
3 inches thick the stone can be spread on the road and treated 
like the top course of a new road. If the course is to be made 
of 3 inches or more of loose stone, it is generally best to loosen 
up the road by means of spikes placed in the wheels of the roller 
or by the use of a scarifier. 

This method of maintenance is practically obsolete on account 
of motor traffic. The shearing action of the wheels of an auto- 
mobile on a water-bound road speedily loosens the stones of the 
top course and it is necessary to protect the surface by a tenacious 
mat of bituminous material and stone. Experience shows that 
this should not be applied until the road has seasoned for a few 
months. If the road is finished late in the fall, so that no oppor- 
tunity will be afforded for it to season before winter closes down 
construction work, the surface can be bound with calcium chlo- 
ride to hold it until spring, when the bituminous mat can be 
applied. 

The ordinary method of maintaining the road is to clean it 
thoroughly and then apply a road oil uniformly over the surface. 
Some of these oils are so thin that they soak into the surface 
while others must be covered with sharp sand or screenings free 
from dust. The methods of doing the work are explained in 
the chapter on surface applications. 



ROAD BUILDING ROCKS 

Mineral Composition} — Reports of geologists and mineralo- 
gists on road-building rocks classify theni according to their 
origin as igneous, sedimentary and metamorphic. 

Igneous rocks are those which have solidified from a very hot 
liquid condition and their physical condition, technically termed 
"structure," depends largely on the rate of cooling of the fused 
material. The ''intrusive" or ''plutonic" type of igneous rocks 
cooled slowly at great depths below the earth's surface, and the 
minerals composing it are usually in large and well developed 
particles. This type includes granite, syenite, diorite, gabbro, 
and peridotite. The ''extrusive" or "volcanic" types of igneous 
rocks cooled more rapidly upon the earth's surface and are finer 
grained. They frequently show a so-called " porphjTitic" 
structiure on account of the presence of larger crystals in a fine- 
grained, dense mass forming the main mass of the rock. This 
type includes rhyolite, trachyte, andesite, basalt and diabase. 

Sedimentary rocks are made up of fragments of minerals or 
shells that were moved about, mainly by water, and finally de- 
posited on the beds of lakes or seas in more or less parallel layers. 
There they became cemented together by the pressure upon them 
and changes in the composition of a part of their constituents. 
This last change is of the same general nature as that occurring 
far more quickly in the case of plaster or mortar. This class 
includes calcareous types of rock like limestone and dolomite, 
and siliceous types like shale, sandstone, and chert (flint). Both 
types are usually distinctly bedded or stratified. 

Metamorphic rocks were produced from the two classes just 
mentioned by pressure and heat. The long-continued shearing 
and compressive forces sometimes produced a "foliated" or 
"schistose" character, with a parallel arrangement of the minerals 
composing them, or a "massive" or "nonfoliated" character. 
Gneiss, schist and amphibolite are foliated metamorphic rocks, 
and slate, quartzite, eclogite and marble are nonfoliated meta- 
morphic rocks. 

^ Abridged from Bulletin 348, U. S. Department of Agriculture, "Rela- 
tion of Mineral Composition and Rock Structure to the Physical Pro^ 
erties of Rock Materials," by E. C. E. Lord, petrographer, Office of Publi* 
Roads and Rural Engineering. 

75 



76 



AMERICAN HIGHWAY ASSOCIATION 







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ROAD BUILDING ROCKS 83 

The original mineral components of igneous rocks and the 
essential part of metamorphic schists are quartz, plagioclase, 
orthoclase, augite, hornblende, muscovite, biotite, rock glass, 
magnetite and garnet. These are called primary minerals. 
Rock glass, included among them, is a mineral of variable com- 
position found in certain volcanic rocks which cooled very rapidly. 
It is extremely brittle and when present in appreciable quantities 
has a tendency to lower the wearing properties of the rock. Orth- 
oclase and plagioclase are usually called "feldspar" by engineers 
and biotite and muscovite are called "mica." 

Quartz is the most widely distributed mineral known. It has 
a specific gravity of 2.66 and a hardness of 7 in Mohs' scale. ^ 
When present in large quantities, especially when finely consoli- 
dated, as in fine-grained, igneous and massive metamorphic 
rocks, the resulting material is extremely hard and offers great 
resistance to wear. 

Orthoclase and plagioclase are among the principal ingredients 
of igneous and metamorphic rocks and some sandstones. Their 
specific gravity is 2.54 to 2.76 and their hardness 6 to 6.5. Many 
coarse-grained feldspathic rocks break down readily under im- 
pact on account of the cleavage of these minerals. In fine- 
grained rocks the effect of this cleavage is less marked, and some 
of them are extremely hard and tough. 

Augite and hornblende are the chief iron-bearing or dark silicate 
constituents of basic igneous rocks, commonly called "trap 
rocks," and the crystalline schists derived from them. Their 
specific gravity is 2.93 to 3.71 and their hardness 5 to 6.5. Their 
crystalline shape is such that they interlock very compactly with 
other minerals, which is one of the reasons for the marked dura- 
bility of trap rocks. 

Biotite and muscovite occur chiefly in granite, gneiss and mica- 
ceous schist. Their specific gravity is 2.7 to 3.2 and their hard- 
ness is 2 to 3. The flaky character of mica is well known and is 
largely responsible for the foliated character of many metamor- 
phic rocks and their resulting inferior wearing properties in roads. 

Magnetite has a specific gravity of 5.18 and a hardness of 5.5. 
Garnet has a specific gravity of 3.15 and a hardness of 7.5. They 
occur in only two road-building rocks, peridotite and eclogite, 
and in some cases materially increase the wearing properties of 
the rock. 

Secondary minerals are produced by the alteration of rocks, 
mainly by the chemical action of water and carbonic acid on 
primary rock constituents. The chief secondary minerals are 

^ Mohs' scale of the relative hardness of minerals is as follows: 1, Talc; 
2, gypsum; 3, calcite; 4, fluorite; 5, apatite; 6, orthoclase; 7, quartz; 8, 
topaz; 9, corundum; 10, diamond. 



84 AMERICAN HIQHWAT AgfiOCIATION 

calcite, dolomite, kaolin, chlorite, epidote, limonite, serpentine, 
talc, zeolite and opal. 

Calcite has a specific gravity of 2,6 and a hardness of 3. Dolo- 
mite has a specific gravity of 2.9 and a hardness of 3.5. These 
two minerals are the chief constituents of limestones and dolo- 
mites, and cannot be distinguished microscopically. They 
cleave freely and hence many calcareous rocks break down readily 
when used in roads. 

Kaolin is derived to a large extent through the decomposition 
of orthoclase. It sometimes occurs in small crystal flakes re- 
sembling white mica (muscovite), and sometimes as minute 
grains of very indefinite composition. In the latter form, called 
^'amorphous," kaolin has a great effect on the binding property 
of rock powders, for it becomes glue-Hke when wet, and when 
dry it binds together firmly the other mineral particles with 
which it is associated. 

Chlorite and epidote are derived from augite, hornblende, 
biotite and plagioclase and are most abundant in trap rocks and 
dark crystalhne schists. Chlorite is a soft green mineral which 
occurs either in mica-like flakes or as very fine scales and fibers of 
indefinite composition. In the latter form it has cementing 
properties like those of amorphous kaoUn. Epidote (specific 
gravity, 3.25-3.5; hardness, 6-7) occurs as yellowish green crystals 
which, when present in appreciable quantities, apparently in- 
crease the wearing properties of rocks. 

The results of a study of several hundred road-building rocks 
indicate that the effects of their mineral composition on their 
value for highway purposes are probably as follows : 

Igneous and nonfoliated metamorphic rocks, owing to a pre- 
ponderance of hard sihcate minerals combined with greater uni- 
formity in structure, are more durable than other road-making 
materials, finer-grained varieties offering greater resistance to 
abrasion than coarse-grained types. 

The resistance to wear of igneous and metamorphic rocks, 
containing an abundance of quartz, hornblende, augite, epidote, 
and garnet, is greater than that of similar rocks rich in mica, 
chlorite, serpentine, and calcite. 

Foliated metamorphic rocks, owing to the parallel arrange- 
ment of their mineral constituents, are, as a rule, deficient in 
toughness and therefore not well adapted to road construction. 

Sedimentary rocks are usually deficient in wearing properties, 
except in the case of highly indurated sandstones, containing a 
moderate amount of siliceous clay, cement, and hmestones or 
dolomites rich in quartz and having very httle clay. 

Rocks for road making break down under impact into frag- 
ments, the shape and physical character of which ai'e conditioned 
by mineral composition and structure. 



ROAD BUILDING ROCKS 85 

The effect of weathering is generally to lower the resistance to 
wear of road materials, owing to the development of soft, in 
part glue-Hke (colloidal) products of alteration. Where the 
secondary minerals are harder and more crystalline the wearing 
properties of the rocks are proportionately increased. 

The cementing value of road materials is conditioned chiefly by 
the glue-like (colloidal) products of rock decay and increases in a 
general way proportionately with these products, reaching a 
maximum in rocks free from quartz. 

The slaking property of rock powders is dependent in the case 
of siliceous igneous and metamorphic rocks chiefly on the physical 
character of the primary mineral components, whereas in basic 
igneous rocks and sandstones it is caused to a large degree by 
glue-like (colloidal) products of rock decomposition. 

Physical Properties} — The success or failure of a rock for road 
building depends largely upon the extent to which it will resist 
the destructive influences of traffic. The three most important 
physical properties are hardness, toughness, and binding power 
Hardness is the resistance which the rock offers to the displace- 
ment of its surface particles by abrasion; toughness is the resist- 
ance which it offers to fracture under impact; and binding power 
is the ability which the dust from the rock possesses, or develops 
by contact with water, of binding the large rock fragments to 
gether. In order to approximate as closely as possible in the 
laboratory the destructive effects produced by traffic, climatic 
agencies and faulty construction, certain physical tests have 
been developed. 

Hardness is determined by subjecting a cylindrical rock core 25 
millimeters in diameter, drilled from the specimen to be examined. 
to the abrasive action of quartz sand fed upon a revolving steel 
disk. The end of the specimen is worn away in inverse ratio to 
its hardness, and the amount of loss is expressed in the form of a 
coefficient as follows: 

Coefficient of hardness =- 20 - w/'^, where w equals the loss in 
weight after 1,000 revolutions of the disk. 

Toughness is determined by subjecting a cylindrical test speci- 
men 25 by 25 millimeters in size to the impact produced by the 
fall of a 2-kilogram hammer upon a steel plunger whose lower 
end is spherical and rests upon the test piece. The energy of 
the blow delivered is increased by increasing the height of fall 
of the hammer 1 centimeter after each blow. The height of 
blow in centimeters at failure of the specimen is called the tough- 
ness. 

^Abstracted from Bulletin 370, U. S. Department of Agriculture, "Re- 
sults of Physical Tests of Road Building Rock/' by Prevost Hubbard, 
chemical engineer, and Frank H. Jackson, Jr., assistant chemical engineer, 
OflBce of Public Roads. 



86 AMERICAN HIGHWAY ASSOCIATION 

A test devised by the French and sometimes called the Deval 
test, for measm*ing the combined action of abrasion and impact, 
is as follows: Five kilograms of freshly broken rock between 2 
and 2J inches in size is tested in a special form of cylinder so 
mounted on a frame that the axis of rotation of the cylinder is 
inclined at an angle of 30° with the axis of the cyhnder itself. 
The fragments of rock forming the charge are thus thrown from 
end to end twice during each revolution, causing them to strike 
and rub against each other and the sides of the cylinder. After 
10,000 revolutions the resulting material is screened through a 
T^g-inch sieve and the weight of the material passing is used to 
calculate the percentage of wear. The French coefficient of 
wear is calculated from the per cent of wear as follows: 

French coefficient of wear = 40 -f percentage of wear 

To determine the binding power, or cementing value, as it is 
usually called, 500 grams of the material to be tested is crushed 
to pea size and ground with water in a ball mill until it has the 
consistency of a stiff dough. It is then molded into cylindrical 
briquettes 25 by 25 millimeters in size, which, after thorough 
drying, are tested to destruction in a special form of impact 
machine. A 1-kilogram hammer falls through a constant height 
of 1 centimeter upon an intervening plunger, which in turn rests 
upon the test piece. A graphic record of the number of blows 
required to destroy the specimen is obtained. The number of 
blows producing failure is called the cementing value of the 
material. 

The specific gravity, weight per cubic foot, and the water 
absorption in pounds per cubic foot are obtained on samples of 
rock which are tested to determine their road-building qualities. 
The weight per cubic foot is calculated from the specific gravity 
of the material obtained on a 10-gram sample by the usual dis- 
placement method. The gain in weight of this fragment after 
four days' continuous immersion in water is used to calculate 
the water absorption in pounds per cubic foot of the solid rock. 

Results of Tests. — Because of the fact that the various rock 
families, when subjected to the tests outlined, give results which 
are more or less distinctive of a group or type, these results can 
best be discussed in many cases collectively. There are 14 fam- 
ilies of rock which are more or less commonly used in macadam- 
road construction. The variations which have been found to 
exist in the three principal tests for each of these are shown in 
graphic form in the diagrams on pages 76-82. The values of 
the tests are arranged as abscissse, with the zero points to the 
left and the values numerically increasing toward the right. 



ROAD BUILDING ROCKS 87 

The ordinates or vertical lines represent the percentages of the 
total number of samples having values corresponding to the 
abscissae on which they are plotted. The figures in parentheses 
in the upper right-hand corner of each block represent the total 
number of determinations from which these percentages were 
calculated. 

Andesite, Basalt, Diabase, Diorite, Gabbro, and Rhyolite 
comprise the well-known group of road-building rocks commonly 
known as "trap." The average toughness of all the traps, with 
the exception of gabbro, which runs somewhat lower, is about 18. 
This is a considerably higher average than that shown by any 
of the other types or groups. The same relationship holds true 
in the abrasion test, the average French coefficient of wear run- 
ning from about 13 to 15. Comparatively slight variations in 
hardness are noted for any family or for the group as a whole, 
the average hardness for which is about 18. The binding power 
of the traps varies through wide limits, depending largely on the 
degree of weathering they have undergone. The specific gravity 
of this group averages about 2.9, giving an average weight per 
cubic foot of 180 pounds. Individual samples are seldom less 
than 2.7 nor more than 3.2 specific gravity. Water absorption 
may vary from a few hundredths of 1 per cent to over 7 per cent. 

Granite is characterized by low toughness and high hardness. 
The average value for the former is about 8, while that for the 
latter runs as 18.5. The abrasion test develops an average 
French coefficient of wear of about 11. Cementing values run 
low, the only exceptions being very highly weathered material 
which usually shows low toughness and resistance to wear. The 
specific gravity averages 2.7. The weight per cubic foot aver- 
ages 168 pounds. Water absorption has been found to run from 
about 0.04 to 3 per cent. 

The limestones and dolomites, or magnesium limestones, are 
undoubtedly the most widely used road-building rock. The 
average French coefficient of wear is about 8, toughness 7, and 
hardness 15. The cementing values are usually good, about 75 
per cent of all samples tested running over 25. The specific grav- 
ity of the limestones and dolomites averages close to 2.7. In 
general, the weight per cubic foot will average about 168 pounds 
for the limestones and 170 pounds for the dolomite. Absorption 
may vary from a few hundredths of 1 per cent to over 13 per 
cent. 

The sandstones are characterized by wide variations in the 
results of all tests. The average French coeflficient of wear is 
about 12, average toughness about 10, and average hardness 
about 16. The cementing value of sandstones varies widely, 
depending upon their composition. Their specific gravity aver- 



88 AMERICAN HIGHWAY ASSOCIATION 

ages 2.62. The weight per cubic foot averages 164 pounds. 
Absorption runs from a few hundredths of 1 per cent to about 2 
per cent. 

The average toughness of marble is about 5 and the average 
hardness is less than 14. Marbles usually show good cementing 
value tests, vnth. about the same range as the lunes tones and 
dolomites. The specific gravity ordinarily falls between 2.7 and 
2.9 and the weight per cubic foot averages 173 pounds, which is 
somewhat higher than the average for either limestone or dolo- 
mite. The maximum absorption is under 2.5 per cent. 

Quartzites show an average toughness of 15. The quartzites 
invariably show a low cementing value. Their specific gravity 
usually Ues between 2.6 and 2.8 and their average weight per cubic 
foot is about 167 pounds. Their water absorption runs from a 
few hundredths of 1 per cent to nearly 3 per cent. 

Gneiss and schist show similar physical properties. The 
average French coefficient of wear for the gneiss samples is about 
9. Their average hardness, toughness, specific gravity, weight 
per cubic foot, and absorption are approximately the same as for 
granite. 

The schists show an average French coefficient of wear of about 
12. Their average hardness is about 17.5 and their toughness 
averages 11. The toughness test for both gneiss and schist is 
made perpendicular to the plane of foKation. If taken hori- 
zontal to the plane of fohation much lower results would be ob- 
tained, as failure would then occur along these natural lines of 
cleavage. The specific gravity of schists usually lies between 
2.65 and 2.90 and the average weight per cubic foot is about 181 
pounds. Water absorption is seldom over 2 per cent for this 
family. 

With the exception of the highly altered varieties, both gneisses 
and schists show a rather low cementing value. 

Chert is a very hard material, but frequently shows a low re- 
sistance to wear, owing to its tendency to fracture along lines 
which have developed as shrinkage cracks in the rock structure. 
For this reason it is extremely difficult to test for toughness. The 
cementing value of pure chert is usually low, but some highly 
weathered deposits develop in ser^dce good cementing value, 
especially if a high-binding clay is associated with it. The 
French coefficient of wear has usually been found to average 5, 
toughness 16, and the hardaiess coefficient between 19 and 20. 
Specific gravity usually lies between 2.4 and 2.65 and the aver- 
age weight per cubic foot is about 160 pounds. Water absorp- 
tion may run from a fe^- tenths of 1 per cent to over 8 per cent. 

Shales and slates are highly laminated rocks that tend to break 
into flat plates not suitable for road-building purposes. They 



ROAD BUILDING ROCKS 89 

are seldom used in road construction, except perhaps as a filling 
for sub-foundations. They vary greatly in nearly all of their 
physical properties. 

Many varieties of slag resemble in certain outward respects 
the common road-building rocks. However, in general, they 
are more porous and glassy, and vary so greatly in physical 
properties that with reference to their physical characteristics 
from the standpoint of road construction they cannot well be 
considered as a single class with definite hmits or general average 
numerical values. 



CONCRETE ROADS 

Although concrete pavements were laid at Belief ontaine, Ohio, 
in 1893 and 1894, the type did not attract general attention until 
fifteen years later. During 1913, over 10,000,000 square yards 
were laid, eight times as much as in 1911. This rapid develop- 
ment was accompanied by m.arked differences in methods of con- 
struction, which aroused some apprehension that poor results 
from inferior methods would retard the logical adoption of the 
type in places for which it was suited. Accordingly road and 
street engineers and contractors from all parts of the country 
met in February, 1914, for a three-day discussion of concrete 
road building. The report of this conference exercised a standard- 
izing influence on methods of construction, as had the somewhat 
earlier adoption by the American Concrete Institute of stand- 
ard specifications for concrete roads and pavements. Some of 
the methods of construction presented features which required 
detailed investigation, and committees were appointed for such 
work. In February, 1916, a second national conference was 
held, at which the reports of these committees were received 
and discussed. This chapter summarizes the information pre- 
sented at that conference. 

Foundation and Subgrade 

The following opinions regarding foundations and subgrade 
were adopted by the 1916 conference: 

When roadways are constructed over fills, extreme care should be ob- 
served to insure the use of proper materials in layers of such thickness 
that they may be thoroughly compacted so that when the fill is completed 
there will be a minimum of settlement. In general, fills shall be made in 
thin layers, the depth depending on the character of material to be used 
in making the fill. The fill should be allowed to stand for as long a time 
as possible, giving it an opportunity to settle thoroughly before the pave- 
ment is placed thereon. Deep fills should be allowed to settle through 
one winter wherever such procedure is possible. Puddling will be found 
advantageous in compacting deep fills. Wetting and rolling shall be per- 
formed when making a fill in order to secure thorough compactness. Fills 
should never be made with frozen materials nor with lumps greater than 6 
inches in their greatest dimension. 

The fundamental requirement of the subgrade is that it should be of 
uniform density so that it will not settle unevenly and cause cracks in the 
surface of the pavement. No part of the work is more worthy of intelli- 

90 



CONCRETE ROADS 91 

gent care and painstaking labor than the preparation of the subgrade. The 
slight additional cost necessary to insure good results is abundantly jus- 
tifiable. When the pavement is constructed on virgin soil, care should 
be taken to remove all soft spots so as to insure a uniform density; and if 
constructed on an old roadbed, even greater care must be taken to secure 
uniform density, as the subgrade is likely to be more compact in the cen- 
ter than at the sides. An old roadbed should be scarified, reshaped and 
rolled. The subgrade adjacent to curbs should be hand-tamped. 

The importance of a uniformly firm support for the concrete 
slab was not fully appreciated by all roadbuilders. There was an 
opinion among some that the concrete would act as a beam and 
distribute the loads coming on it over such a wide area that inequali- 
ties in the sustaining power of the earth would prove unimportant. 
The number of cracks in concrete pavements attributable to un- 
warranted confidence in this beam action is beyond proof, but 
today the opinion is generally held that the money spent in se- 
curing a firm foundation is a wise outlay to insure low mainte- 
nance charges. This is particularly the case where an old road 
is used for a foundation. It is unlikely that a concrete pavement 
will be laid on it until the old road needs repairs. If the sur- 
face is then merely leveled by a thin course of stone or gravel, it 
is possible that there will be weak places, particularly along the 
sides of the road. 

Drainage 

The 1916 conference adopted the following statement of the 
principles which should govern the drainage of the roadbed sup- 
porting a concrete slab: 

The drainage of the roadbed is of vital importance. If the subgrade 
is not well drained there is danger of unequal settlement and of frost action, 
which will cause cracks. The method of drainage to be used will depend 
on local conditions. For streets, as well as roads, tile drains may be used 
which should be laid on each side of the roadway, or on one side only, 
with cross-drains leading thereto at a suitable depth, depending on the 
width of the pavement. Drainage trenches, if placed under the subgrade, 
should be completed before final rolling. 

There is an objection to the use of cross-drains under thin 
concrete roads w^hich is not serious in most cases but may be 
under some conditions. It is practically impossible to compact 
the miaterial over a blind drain as thoroughly as that of the main 
portion of the subgrade, and each blind drain is likely to be a weak 
place in the foundation. An alternative for them which some 
engineers hnve advised is the construction of a blind drain just 
outside each edge of the concrete slab and extending 8 or 10 
inches below the subgrade. These drains are connected every 
50 feet with the side ditches by blind drains. All drains under 



92 AMERICAN HIGHWAY ASSOCIATION 

the roadway should have a covering of sand or fine gravel on 
top to prevent the mortar in the wet concrete from passing into 
the broken stone or gravel of the drain. 

Cross-section of Roads 

The following statements were adopted by the 1916 conference 
regarding the section of the concrete pavement : 

The thickness of a concrete road or pavement is controlled by many 
factors, each of which should be given consideration. In view of the in- 
creasing use of the heavy motor truck and bus, it seems unwise to build 
pavements with a thickness of less than six inches at any point. In gen- 
eral, pavements should be thicker at the center than at the sides. Alleys 
with an inverted crown, and narrow one-slope roads, should have a uni- 
form thickness. Wherever the thickness can be increased without excess- 
ive cost, to secure a flat subgrade, or one nearly flat, such increase is 
advisable. 

The desirable width for single-track roads is 10 feet. The desirable 
width of double-track roads is 18 feet. The total width of the roadway 
should not be less than 20 feet for single-track roads and not less than 26 
feet for double-track roads. 

The crown of roads and pavements should be not less than one one- 
hundredth nor more than one -fiftieth of the total width. Except in un- 
usual cases, one one-hundredth will be suflficient for country roads and one- 
fiftieth will be considered satisfactory for alley pavenents. For city 
streets an average crown of one -seventy-fifth will generally be found 
sufficient and should not be reduced, except on grades. 

Single-track concrete roads are occasionally built on the right- 
hand side of the roadway going in the direction of the heavy 
traffic. This gives the loaded wagons the better surface. The 
templet used in determining the section of the road is the same 
as for a double-track road but only one-half the road is concreted. 
In Huron and Medina Counties, single-track roads have been 
built as one-slope roads instead of half the section of double-track 
roads, and this construction is preferred by some engineers. 

In Wayne County, Michigan, it has been decided to make 
concrete roads 18 feet wide wherever possible, and never less 
than 16 feet. Near Detroit the width will be 20 feet. While 
this increase in width from 10, 12, 15, and 16 feet will add 
materially to the first cost, it is expected to prove economical 
in the long run, because the expense of maintaining heavy broken 
stone or gravel shoulders will be avoided. This maintenance is a 
large sum on comparatively narrow roads with heavy traffic. 

There is a decided difference of opinion regarding shoulders 
for concrete roads. Some engineers hold that the natural soil 
should be used, and where satisfactory shoulders cannot be 
made of it the width of the concrete should be increased. Other 
engineers recomm.end gravel or broken stone shoulders after 



CONCRETE ROADS 93 

experience with them. The difference of opinion is probably 
due to differences in the quahty of the earth which must be 
used for earth shoulders and to differences in the character of the 
traffic, upon which the opinions are based. There is no question, 
however, that if traffic makes frequent use of shoulders of clay 
or clayey loam, they are speedily ruined, and if heavy traffic makes 
frequent use of macadam shoulders, the junction between the 
concrete and broken stone becomes a long rut. In either case the 
proper maintenance of the shoulders will be expensive. If two 
macadam or gravel shoulders wider than 4 feet are considered 
necessary, it is advisable in every case to consider the alternative 
of an increased width of concrete. The construction of gravel 
and macadam shoulders should be postponed, if practicable, until 
a month after the concrete road has been finished, and they should 
be left slightly higher than the concrete to facilitate turning 
out on them. 

In cuts, where the grades are over 5 per cent, it is usually neces- 
sary to pave the ditches and to use gravel or macadam shoulders. 
The maintenance of these ditches and shoulders is expensive, 
and it is possible that money will be saved in the end, even on 
single-track roads, by increasing the width of the concrete and 
adding a concrete ditch and curb at each side. The ordinary 
construction will call for a 10-foot concrete road, 8 feet of shoul- 
ders and 8 feet of ditches, a total of 26 feet width of cut at the 
bottom of the excavation. For this can be substituted a concrete 
roadway 16 feet wide with two integral curbs bringing the total 
width to 17 feet 8 inches. The curb acts as an abutment for the 
toe of the slope. 

On fills over 5 or 6 feet high, where turning out on a soft shoulder 
may cause a serious accident, it is desirable to widen a single- 
track pavement to 16 feet unless the top of the fill is so wide that 
an overturned car will not roll down the slope. In any such case, 
the safety of the public requires a more careful study of the 
dangers on embankments than was given to the subject before 
automobiles became numerous. Attention is called to the 
record of deaths and injuries on page 25. 

Materials 

Cement is bought for most road work under the standard 
specifications of the American Society for Testing Materials, 
which were revised in 1916. They are printed in the next chapter. 

The following statements regarding fine and coarse aggregate 
were adopted by the 1916 conference: 

The selection of proper aggregates for concrete road construction is 
of utmost importance. Clean, hard, well-graded materials are absolutely 



94 AMERICAN HIGHWAY ASSOCIATION 

essential to success. For this reason samples of the materials proposed 
for use should be submitted to the engineer for approval before orders 
are placed. These samples should be carefully inspected; and if possible 
laboratory tests made to determine their suitability. If laboratory tests 
on shipments cannot be made, field tests can be used to furnish a general 
indication of quality. 

The different aggregates should be kept clean and separate. 

Aggregates to be used in the wearing course of two-course pavements 
should never be placed on the subgrade but on planks or some other means 
provided to keep them free from dirt. When aggregates are placed di- 
rectly on the subgrade care should be used by the shovelers to avoid get- 
ting clay or earth shoveled from the subgrade into the mix. Aggregates 
should not only be clean when they are delivered on the job, but clean 
when placed in the mixer. 

Investigations to determine the usefulness of the rattler test 
to show the value of different concrete mixtures for road work 
indicate that it may prove of value. For the present, however, 
the older practice of relying on tests of the stone is being followed 
wherever any testing is done. Generally the best clean, hard and 
tough crushed rock or gravel is used, provided it will give a con- 
crete harder than the mortar used with it. It is desirable to 
use stone having a French coefficient of wear of at least 8. 

Experience indicates that cracks occur more often in gravel 
concrete than in stone concrete. Probably this is largely due 
to the very fine material on the surface of most gravel pebbles, 
which must be washed off carefully to make the material fit for 
road work. 

Fine aggregate, or ''sand," is generally required to pass a J- 
inch screen. Not more than 25 per cent must pass a 50-mesh 
sieve and not more than 5 per cent a 100-mesh sieve. It must 
contain no vegetable or other deleterious matter and not over 3 
per cent by weight of clay or loam. The sand should be tested 
frequently in the field by shaking a sample with water in a grad- 
uated glass and allowing it to settle for an hour. If there 
is more than about 5 per cent of very fine material showing on the 
top of the sand, samples should be sent to the laboratory. Nat- 
ural sand or screenings from hard, tough, durable rock may 
be used. Natural sand sometimes contains vegetable acids 
which reduce its value for good concrete. Their presence is 
determined by making similar briquettes of the natural sand 
and of standard Ottawa sand, and no natural sand should be used 
in road work which does not give a strength at least equal to 
that obtained with Ottawa sand. The best sand is that in which 
the coarse particles predominate. Improvements can sometimes 
be made by mixing two natural sands or a fine sand and screenings. 

The standard specifications for coarse aggregate, or ''stone" 
call for material passing a 2-inch round opening, with not more 



CONCRETE ROADS 95 

than 5 per cent passing a screen having four meshes per inch 
and without any intermediate sizes removed. 

The water used in making the concrete must be free from oil, 
acid, alkali or vegetable matter. 

Proportions 

The 1916 conference adopted the following statements of the 
principles governing the proportions of the materials: 

The method of measuring materials for the concrete, including water, 
should be one which will insure accurate proportions of each of the in- 
gredients at all times. It is recommended that a sack of Portland ce- 
ment, containing 94 pounds net, be considered the equivalent to 1 cubic 
foot. 

The proportions should not exceed 5 parts of fine and coarse aggregate 
measured separately to 1 part of Portland cement, and the fine aggregate 
should not exceed 40 per cent of the mixture of fine and coarse aggregates. 

The standard specifications for one-course country roads call 
for one sack of cement to not more than 2 cubic feet of fine aggre- 
gate and not more than 3 cubic feet of coarse aggregate, with 
the volume of fine aggregate never less than half that of the 
coarse aggregate. A cubic yard of the mixed concrete must 
contain at least 1.7 barrels of cement. The amount of water 
used must be enough to produce concrete holding its shape 
when struck with a template. Concrete which has partly hard- 
ened must never be used. 

The standard specifications for two-course pavements call 
for a base m.ixed in the proportions of 1 sack of cement to not 
more than 2§ cubic feet of fine aggregate and not more than 4 
cubic feet of coarse aggregate, with at least half as much fine as 
coarse aggregate. Two grades of top aggregate are specified 
for the top course; No. 1 must pass a J-inch screen and have not 
over 10 per cent passing a J-inch screen, and No. 2 must pass a 
1-inch screen and have not over 5 per cent passing a J-inch 
screen. Two mixtures are specified for the top course. Mix- 
ture 1 consists of one sack of cement to not more than 1 cubic 
foot of fine aggregate and not more than IJ-cubic feet of No. 
1 top aggregate. Mixture 2 consists of one sack of cement 
to not more than IJ cubic feet of fine aggregate and not more 
than 2 1 cubic feet of No. 2 top aggregate. The volume of fine 
aggregate must equal half the volume of top aggregate in either 
mixture. 

The quantities of cement, sand and gravel required to build 
a mile of road of different widths and thicknesses are given in the 
accompanying tables, supplied by the Portland Cement Associa- 
tion. They are based on the assumption that a barrel of cement is 



96 



AMERICAN HIGHWAY ASSOCIATION 



equivalent to 4 cubic feet and the voids in the stone are 45 per 
cent. Variations from the tabulated quantities may amount 
to 10 per cent either way. 

The proportions of cement, sand and stone should be such 
that the concrete will have the properties desired for a road. 
Where good stone is expensive but softer stone is cheaper, a two- 
course pavement utilizing the poor stone in the base and the hard 
stone in the top may prove more economical than a thinner one- 

Quantities of Cement, Sand and Stone Required for One Mile of Single- 
Course Concrete Road of Different Widths and Thicknesses 









{Furnished by the Portland Cement Association) 










THICK- 
NESS 


AREA 

CROSS 

SECTION 


SUPER- 
FICIAL 
AREA 


VOLUME 
CON- 
CRETE 


mix; 1: 2:4 


mix; 1:2: 3 


Mix; 1: ly. 3 


n 

o 

M 


o 
ins. 

5 
6 
5 
6 
5 
5 
6 
6 
5 
6 
5 
6 
5 
6 
5 
6 
5 
6 
5 
6 


a 

V 

U 


4.3 

a 

O 




1 


§ 

i 


c 


1 


•1-9 

a 

a 

O 


a 


§ 

■ta 


ft. 

10 
10 
12 
12 
14 
14 
14 
14 
16 
16 
18 
18 
20 
20 
22 
22 
24 
24 
30 
30 


ins. 

6i 

7i 

6^ 

7h 

6f 

7 

7f 

8 

7 

8 

7i 

8i 

7i 

8^ 

5 

6 

5 

6 

5 

6 


sq. yds. 

0.540 
0.633 
0.667 
0.778 
0.799 
0.821 
0.929 
0.951 
0.938 
1.086 
1.083 
1.250 
1.235 
1.420 
1.019 
1.222 
1.111 
1.333 
1.389 
1.667 


sq. yds. 

5,867 

5,867 

7,040 

7,040 

8,213 

8,213 

8,213 

8,213 

9,387 

9,387 

10,560 

10,560 

11,733 

11,733 

12,907 

12,907 

14,080 

14,080 

17,600 

17,600 


cu. yds. 

951 
1113 
1173 
1369 
1407 
1445 
1635 
1673 
1651 
1912 
1907 
2200 
2173 
2499 
1794 
2151 
1955 
2346 
2444 
2934 


bbls. 

1436 
1680 
1771 
2067 
2125 
2182 
2469 
2526 
2493 
2887 
2880 
3322 
3281 
3773 
2709 
3248 
2952 
3543 
3690 
4430 


CU. 

yds. 

428 
496 
521 
608 
625 
650 
728 
753 
735 
851 
849 
979 
967 
1112 
798 
957 
870 
1044 
1087 
1305 


cu. 
yds. 

856 
991 
1043 
1218 
1250 
1298 
1455 
1504 
1469 
1702 
1697 
1958 
1934 
2224 
1597 
1914 
1740 
2088 
2175 
2611 


bbls. 

1654 
1938 
2040 
2382 
2448 
2514 
2845 
2911 
2873 
3327 
3318 
3828 
3781 
4348 
3122 
3743 
3402 
4082 
4253 
5105 


CU. 

yds. 

494 

578 

610 

710 

732 

751 

850 

870 

859 

994 

992 

1144 

1130 

1300 

933 

1119 

1017 

1220 

1271 

1526 


CU. 

yds. 

732 
856 
903 
1054 
1084 
1113 
1259 
1288 
1271 
1472 
1468 
1694 
1673 
1924 
1381 
1656 
1505 
1806 
1882 
2259 


bbls. 

1818 
2124 
2240 
2614 
2685 
2760 
3121 
3195 
3153 
3652 
3642 
4202 
4150 
4773 
3426 
4108 
3734 
4482 
4670 
5603 


CU. 

ydk. 

405 
473 
498 
582 
597 
607 
695 
703 
702 
813 
810 
935 
924 
1062 
762 
914 
831 
997 
1038 
1247 


CU. 

yds. 

809 
946 
997 
1164 
1195 
1228 
1390 
1422 
1403 
1625 
1621 
1870 
1847 
2124 
1525 
1828 
1662 
1994 
2077 
2494 



course pavement of the harder stone. In any case the amount 
of mortar used should be about 10 per cent in excess of the voids 
in the stone. There is so much variation in the grading of sand 
and stone that a 1:2:4 mixture in one place may be equal to a 
1:2:3 mixture in another. As the work progresses, the quality 
of the concrete must be watched carefully, and the proportions 
shifted so that the greatest density will be obtained. Attention 
to this feature of the work is considered very important by ex- 
perienced concrete road builders. 



CONCRETE ROADS 



97 



Quantities of Cement, Sand and Stone in One Mile of Two-Course Concrete Road of 

Different Widths and Thicknesses 











{Furnished by the Portland Cement Association, 












BASE 


K 
o 

J5 


BASE mix; 1: 2}: 4 


BASE mix; 1:2: 4 


TOP 


u 

H 

a 
o 


TOP Mix; IJ: 2§ 


TOP Mix; 1: 1: li 




Thick- 














Thick- 
















ness 


U 














nes8 


o 














t 

M 


T3 


O 
<» 


a 
o 


a 

a 


a 
a 


03 

CI 

2 


a 
S 


T3 

C 


e 
a 
o 


® 

73 


a 


.J 
o 


a 

a 


a 
a 


a 
o 


g 

a 


13 

a 

C9 


o 
a 

2 


^ 


03 


u 


> 


u 


CO 


Xfl 


u 


m 


M 


02 


U 


> 


O 


M 


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1247 


2005 


3692 


1100 


2176 


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977 


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454 


756 


2902 


429 


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10 


4 


5i 


787 


1094 


401 


645 


1188 


354 


700 


2 


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326 


682 


152 


253 


968 


143 


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951 


1322 


485 


780 


1436 


428 


846 


2 


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326 


682 


152 


253 


968 


143 


215 


12 


4 


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977 


1358 


498 


801 


1475 


440 


870 


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1161 


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12 


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1173 


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598 


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172 


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600 


965 


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1048 


2 


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456 


955 


212 


354 


1355 


200 


303 


14 


5 


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1407 


1956 


718 


1154 


2125 


633 


1254 


2 


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456 


955 


212 


354 


1355 


200 


303 


14 


4 


6 


1216 


1690 


620 


997 


1836 


547 


1082 


2 


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456 


955 


212 


354 


1355 


200 


303 


14 


5 


7 


1445 


2009 


737 


1185 


2182 


650 


1286 


2 


2 


456 


955 


212 


354 


1355 


200 


303 


16 


4 


6 


1392 


1935 


710 


1141 


2102 


626 


1239 


2 


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523 


1091 


243 


404 


1546 


228 


346 


16 


5 


7 


1651 


2295 


842 


1354 


2493 


743 


1469 


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523 


1091 


243 


404 


1546 


228 


346 


18 


4 


6J 


1612 


2241 


822 


1322 


2434 


725 


1435 


2 


2 


586 


1226 


272 


454 


1739 


257 


390 


18 


5 


7\ 


1906 


2649 


972 


1563 


2878 


858 


1696 


2 


2 


586 


1226 


272 


454 


1739 


257 


390 


20 


4 


6^ 


1846 


2566 


941 


1514 


2787 


831 


1643 


2 


2 


651 


1362 


302 


504 


1935 


286 


429 


20 


5 


74 


2174 


3022 


1109 


1783 


3283 


978 


1935 


2 


2 


651 


1362 


302 


504 


1935 


286 


429 


20 


4 


4 


1304 


1813 


665 


1069 


1969 


587 


1161 


2 


2 


651 


1362 


302 


504 


1935 


286 


429 


20 


5 


5 


1630 


2266 


831 


1337 


2461 


734 


1451 


2 


2 


651 


1362 


302 


504 


1935 


286 


429 


22 


4 


4 


1434 


1993 


731 


1176 


2165 


645 


1276 


2 


2 


716 


1498 


333 


555 


2128 


315 


472 


22 


5 


5 


1793 


2492 


914 


1470 


2707 


807 


1596 


2 


2 


716 


1498 


333 


555 


2128 


315 


472 


24 


4 


4 


1563 


2173 


797 


1282 


2360 


703 


1391 


2 


2 


781 


1634 


363 


605 


2322 


343 


515 


24 


5 


5 


1955 


2717 


997 


1603 


2952 


880 


1740 


2 


2 


781 


1634 


363 


605 


2322 


343 


515 


30 


4 


4 


1955 


2717 


997 


1603 


2952 


880 


1740 


2 


2 


977 


2043 


454 


756 


2902 


429 


644 



Mixing 

The principles that should govern mixing were stated as fol- 
lows by the 1916 conference: 

The ingredients should be naixed in a batch mixer. The mixing should 
be continued for at least one minute after all the materials are in the mixer 
and before any of the concrete is discharged. The speed of the mixer 
should not exceed 16 revolutions per minute; however, the time and not 
the number of revolutions should be the gage of proper mixing. 

The practice is to mix concrete entirely too wet. The consistency 
should be such as not to require tamping, but not so wet as to cause the 
separation of the mortar from the aggregate in handling and placing. The 
strength and wearing qualities of the concrete are vitally lessened by an 
excess of water in mixing. 

The reason for fixing one m nute as the minimum time for 
mixing is that tests have shown that water is not worked through 



98 AMERICAN HIGHWAY ASSOCIATION 

the mass as it should be in less than a minute. A smaller quan- 
tity of wat r can be used with long-time mix ng than with short- 
time mixing and the same degree of fluidity obtained. On ac- 
count of the desirability of keeping the amount of water as close 
as possible to 1 gallon per cubic yard of concrete, at least one 
minute m"xing time is desirable. If a large quantity of water 
is used and the mixing time is less than a minute, the product 
may appear uni orm to the eye when it actually is not well mixed. 
The reason for restricting the speed of the mixer to 16 revolu- 
tions per minute is that at a higher speed some of the material 
sticks to the drum and there is considerable splashing as the 
concrete is discharged. At least 10 revolutions are necessary 
to mix the aggregate. 

Placing 

The principles governing placing were stated as follows by the 
1916 conference: 

If the subgrade has been disturbed by teaming or other causes, it should 
be brought to its former surface, and thoroughly moistened with water. 
The concrete should be deposited rapidly to the required depth and width. 
The section should be completed to a transverse joint, with the use of 
intermediate forms or bulkheads, or a transverse joint may be placed at 
the point of stopping the work. In case the mixer breaks down the concrete 
should be mixed by hand to complete the section. Where reinforcement 
is used it should be embedded in the concrete before the concrete has begun 
to harden ; the concrete above the reinforcement should be placed within 
20 minutes after the placing of the concrete below. 

In two-course pavements the top should be placed within twenty min- 
utes after the placing of the bottom. 

The standard specifications allow forty-five minutes as the 
maximum time between the laying of the bottom course and the 
placing of the top course. 

Practically all concrete roads are built with special paving 
mixers which discharge the concrete on the road where it is to 
be used by means of chutes or buckets hauled along a boom that 
can be swung from one side of the road to the other. The pitch 
of the chute should be steep enough to deliver concrete of a 
proper consistency readily. In the attempt to cover consider- 
able area, contractors sometimes set the chute at a flat angle 
and use too much water, in order to make the concrete flow 
readily. Tests have shown that the least angle of the chute 
should be 20 degrees. If the chute is new or rusted, concrete 
with a proper amount of water will flow rather slowly down a 
20 degree slope until the metal surface has been smoothed by the 
wet mass. For this reason the chute may need a steeper slope 
at the outset than later. 



CONCRETE ROADS 99 

Forms 

The 1916 conference adopted the following statement of the 
principles that should govern the use of forms to retain the con- 
crete at the sides of the roadway: 

Metal forms of sufficient strength to withstand the necessary hard 
usage are preferred. When wooden forms are used they should be of at 
least 2-inch stock and capped with a 2-inch angle iron, so constructed that 
adjacent sections can be lapped. Forms should have a width not less 
than the thickness of the pavement at the sides. Particular care should 
be exercised to see that the top edges of forms are clean so as to avoid un- 
evenness in the finished pavement. If forms are warped or stakes not 
properly placed, a poor alignment of the edge of the concrete slab will 
result. 

They must be set firmly and the topes must be true to grade, 
because they support the templets, bridges and other appliances 
used in finishing the surface. The steel angles on wood forms 
are necessary to enable the finishing work to proceed in a satis- 
factory manner. By having the angles project 3 or 4 inches 
beyond the end of the wood at one end and set back the same 
distance at the other, the alignment of the forms will be facili- 
tated. Painting wood forms will prevent warping and add to 
their life. Where a power-driven striking and finishing machine 
is used, specially heavy forms securely held in place are needed. 

Joints 

While transverse joints are omitted on some work, they are 
generally required because of the prevailing opinion that they 
reduce the cracking of the concrete. They are constructed by 
placing across the road a strip of prepared filler made for the 
purpose. This filler is usually held in place by a steel templet 
until the concrete is deposited against it. The templet is then 
removed and the concrete settles against the filler. The joints 
are of two types, with and without metal protection plates. The 
following statements regarding them were adopted at the 1916 
conference : 

Transverse joints should be placed across the pavement perpendic- 
ular to the center line about 50 feet apart. There seems to be a tendency 
to lengthen the distance between joints. Joints should extend entirely 
through the pavement, as well as through the curb if integral curbs are 
used. Joints should be constructed perpendicularly to the surface of the 
pavement to avoid the possibility of one slab rising above the other. 

The tendency of present practice is toward the omission of metal 
protection plates for joints. It is possible that the value of metal pro- 
tection plates is dependent somewhat on the character of the aggregate 
used, and it is considered that they are more essential in street pavements 
than in country highways. 



100 AMERICAN HIGHWAY ASSOCIATION 

The standard specifications call for J-inch transverse joints 
at intervals of not more than 36 feet. The filler must project 
at least |-inch above the concrete during construction, and after 
the completion of the pavement it is trimmed off |-inch above 
the surface. The traffic flattens out the projecting material and 
hardens the top of the joints. Experience shows that it is very 
desirable to have the joints form a plane surface perpendicular 
to the surface of the road. 

Measurements of the expansion and contraction of concrete 
roadway slabs have been made by R. J. Wig, C. S. Laubly and 
W. A. Mclntyre, from which they drew the following conclu- 
sions: Contraction and expansion are caused by both temper- 
ature changes and changes in moisture conditions, and under 
climatic conditions similar to those at Washington, D. C, the 
effects from these two factors in concrete road surfaces are ap- 
proximately of the same magnitude. In concrete roads, ex- 
pansion and contraction are sufl&cient to cause frequent trans- 
verse cracks unless joints are provided. The actual movement 
in any particular case depends upon the character of the concrete 
and of the subgrade. A sloppy concrete shows greater movement 
than a concrete mixed only moderately wet. 

Organization of the Work 

In order for the work to proceed economically, it is necessary 
for the mixer to be kept running most of the time. This can 
only be accomplished if repair parts are kept on hand and mate- 
rials are supplied as needed. If the materials are delivered by 
rail it often pays to keep men at the sand and stone plants to see 
that the railroads furnish cars as needed and the shipments are 
made on time. If the contractor operates his quarry he must 
see that precautions are taken to reduce delays due to break- 
downs or other causes to a minimum. The delivery of mate- 
rials along the road calls for careful planning of both plant and 
organization. In any case, provision should be made against de- 
lays due to insufficient materials by storing supplies of cement, 
sand and stone on the work. The cement can be stored in a shed 
at the railroad siding or in tents with raised wood floors along the 
road. The sand can also be stored along the road. The stone is 
best stored at the railroad siding, because it is costly to rehandle 
and by doing the work at one place mechanical appliances can be 
used which will reduce the expense materially. The organiza- 
tion should be arranged to avoid all unnecessary handling of 
materials, not only because this involves a labor charge but also 
because transportation equipment is doing no useful work while 
being loaded or unloaded. Tractors with trailers, motor trucks 



CONCRETE ROADS 101 

and industrial railways are generally used for hauling, and by 
having competent repairmen to keep them in order and running 
them with two shifts so as to use them about eighteen hours a 
day, very low unit costs are often obtained in comparison with 
the expense of hauling by horses or mules. 

The water supply must be planned to wet the subgrade, sup- 
ply the mixer and keep the concrete wet for a number of days 
after it is laid. While it has been delivered along the road in 
tanks, it is usually pumped through a pipe, generally 2 inches in 
diameter. As the water which must be used sometimes con- 
tains sand which will score the cylinders or plungers of a high 
pressure pump so as to put it out of service, it is often lifted by a 
centrifugal pump in such cases into a storage tank where the sand 
has an opportunity to settle before the water is drawn by the 
high-pressure pump. If the tank has two chambers separated 
by a partition running nearly up to the water level, the separa- 
tion of the sand will be improved, for the stream water can be 
delivered into one chamber where most of the sedimentation 
will occur and be drawn from the other. There should be a relief 
valve in the pipe line near the pressure pump so as to prevent 
breaking the pipe if all the gates on it are closed. If no valve is 
used the pump should be belt driven, so that in case the pressure 
rises the belt will slip. The friction head in a 2-inch pipe when 
discharging 50 gallons per minute is about 85 feet per 1000 feet 
of its length, and when discharging 60 gallons per minute the fric- 
tion head is about 115 feet. Consequently the pump must have 
power to overcome a considerable pressure due to friction as well 
as that due to the highest elevation to which the water must 
be raised. 

The size of the paving gang will depend upon the size of the 
mixer, which should depend in turn upon the rate at which mate- 
rials can be delivered to it. There are two^ sizes of mixers, one 
in which two sacks of cement are used in each batch of concrete 
and the other taking a three-sack batch. The smaller machine 
requires about two men handling cement, two shovelers and two 
wheelers for sand, three shovelers and three wheelers for stone, 
a helper at the mixer and a man to bundle the cement sacks. 
The larger machine requires about two men to handle cement, 
three shovelers and three helpers for sand, four shovelers and 
four wheelers for stone, a helper at the mixer and a man to bundle 
sacks. In addition the crew requires a foreman, a mixer oper- 
ator, a fireman, two men setting forms, a pump tender, three or 
four men spreading and floating the concrete, two finishers, and 
one or two attending to the curing of the concrete. To keep 

' During 1916, four-sack mixers were used on several roads, so it is prob- 
able that there will be three sizes of mixers in regular use soon. 



102 AMERICAN HIGHWAY ASSOCIATION 

such a gang working efficiently in the comparatively small area 
occupied by a concreting job it is necessary to have the mate- 
rials deposited so they can be handled expeditiously and without 
confusion. 

Finishing 

The principles which should govern the finishing of concrete 
were stated as follows by the conference: 

The surface of the concrete should be struck off by means of a templet 
moved with a combined longitudinal and transverse motion. The excess 
material accumulated in front of the templet should be uniformly distrib- 
uted over the surface of the pavement except near the transverse joint, 
vrhere the excess material should be removed. 

The concrete adjoining the transverse joint should be dense and any 
depressions in the surface should be filled with concrete of the same com- 
position as the body of the work. After being brought to the established 
grade with a templet, the concrete should be finished, from a suitable 
bridge, with a wood float to true surface. A metal float should not be 
used.^ 

Brooming of the surface is not necessary and grooves are objectionable 
even on grades. 

For country roads the templet or strikeboard is often made 
of two 2 by 10-inch planks 1 foot longer than the road is wide. 
The lower edge is cut to the desired crown of the road and shod 
with a strip of \ by 4-inch steel fastened with countersunk screws. 
It has a handle on each side at each end, so it can be moved along 
easily with a kind of sawing motion. This motion fills all de- 
pressions with concrete and has no tendency to drag out the 
large stone. A slight excess o ; concrete is always kept ahead 
of the strikeboard, and a workman often walks in front of the 
board to spread the concrete and take care of any excess that 
may accumulate in front of it. It is usually necessary to run the 
strikeboard over the surface three times; with very angular stone 
it may be necessary to go over it four times. 

Finishing is now regarded as very important. At Sioux City, 
Iowa, where the concrete streets are unusually free from cracks, 
the success with this type of roads is attributed to the special care 
spent in the finishing. A wood float is preferred to a steel trowel 
for finishing because it is believed to make a more dense surface 
which is not slippery. The bridge from which the men work 
is a 2 X 12-inch plank, trussed to prevent deflection and supported 
by the side forms. No finishing should be done while there is 
free water on the surface. For finishing at unprotected joints a 
float split lengthwise, so as to fit over the joint filler, is used. 

^ Owing to the rapid development of belt finishing it is probable that finish- 
ing by wood floats will not be considered essential by many engineers after 
this year. 



CONCRETE ROADS 103 

Power finishing machines are now used to some extent as a 
substitute for hand finishing. They operate by rapidly increas- 
ing and decreasing the weight on the area of concrete on which 
they rest. These vibrations of load joggle the concrete, increas- 
ing its density and leaving a satisfactory finish when the con- 
crete has a suitable consistency and the work is conducted 
carefully. 

During 1915 and 1916, an increasing use has been made of 
belt finishing. The work is done with canvas belts from 12 to 
24 inches wide. In Wa>Tie County, Michigan, where the method 
has been used for the longest time, a 12-inch belt about 1 foot 
longer than the width of the road, is preferred. It has a handle 
at each end and is pulled gently back and forth across the surface 
after the latter has been shaped by the strikeboard. After the 
surface is finished in this way, it is gone over a second time with 
another belt, and sometimes a third time with a third belt. The 
belts are washed at the close of each day. 

When belts are used for finishing it is desirable to shape the 
concrete with a strikeboard having a face about 8 inches wide and 
long handles like those of a plow at each end. With such a strike- 
board the men can tamp as well as shape the concrete, and thus 
leave the surface in better condition for the belt than is the case 
with a thin strikeboard. 

Curing 

The protection and curing of the concrete must be carried on 
carefully because the best concrete may be seriously damaged 
by too rapid drying out of the surface in hot or windy weather, 
by exposure to low temperature or by being opened to trafiic too 
soon. The principles which should govern the work were stated 
as follows by the 1916 conference: 

Even the best concrete may be seriously damaged by too rapid drying 
out, early exposure to low temperature, or by being opened to traffic at too 
early a period. Hot sun and drying winds are most liable to dry out the 
concrete too rapidly, thus causing shrinkage cracks or causing a surface 
which will not wear well under traffic. The use of a canvas covering will 
be found effective in overcoming this condition. 

Sprinkling should also be employed as soon as the concrete is hard enough 
to prevent the surface being pitted. An earth covering or protection by 
ponding should be employed after the first day. Under most favorable 
conditions such protection should be given the pavement for at least two 
weeks. Water should be added during this period to keep the concrete 
wet. 

In cool weather it is often advisable to omit the earth covering, thus 
allowing the concrete to harden more rapidly. Sprinkling should not be 
omitted during the day in case the surface shows a tendency to dry out. 
When there is danger of frost, sprinkling should be omitted and a covering 
of canvas or straw and canvas used. 



104 AMERICAN HIGHWAY ASSOCIATION 

Placing concrete in roads and pavements in temperatures at or near 
freeziDg is not advisable, and if in special cases, such work is unavoidable, 
the water and aggregate should be heated and precautions taken to pro- 
tect the concrete from freezing for at least ten days. 

Chemicals to lower the freezing temperature of the mixture should not 
be used. Concrete should not be deposited on a frozen subgrade. 

The canvas provided for protection during hot and windy 
weather, should be sufficient to cover at least half the surface 
laid during a day. Strips 2 yards wide are used and they are 
about a yard longer than the width of the pavement so that each 
end can be weighted. They are supported on frames so as not 
to touch the concrete, and are kept in place until the concrete 
has hardened. 

The curing of concrete by ponding is not only more econom- 
ical in many cases than the use of wet earth but it has a greater 
advantage in permitting the inspector to determine at a glance 
if the curing is proceeding properly. It is difficult to make cer- 
tain that an earth covering is kept properly wet, but there can 
be no question whether water is standing on the concrete. Banks 
of earth are constructed along each edge of the pavement and 
transverse banks at each expansion joint and more frequently 
where the grades make them necessary. The water is kept at 
least 2 inches deep over the center of the road. 

If there is danger of a heavy storm which will pit the surface 
of fresh concrete it must be protected by canvas. Contractors 
are advised to request the nearest forecasting station of the United 
States Weather Bureau to send its daily bulletin of the prob- 
able weather conditions during the next thirty-six hours. 

The standard specifications require both water and aggre- 
gates to be heated if the temperature drops to 35 degrees or is 
likely to do so within twenty-four hours, and the concrete laid 
under these conditions must be specially protected from freezing 
for at least ten days. A canvas cover will be sufficient to pro- 
tect the concrete against frost during the first night and after 
that about 3 inches of straw or marsh hay held down securely 
will probably serve. If a sharp lowering of the temperature is 
anticipated the straw should be covered with canvas. It is 
cheaper to take all necessary precautions than to tear out and 
replace damaged concrete. Even a light freezing of the top 
will make the surface scale. 

Maintenance 

The following explanation of methods of maintenance was 
prepared by A. H. Hinkle, L. C. Herrick, John W. Mueller and 
Mauric© Hoeffken for the 1916 conference: 



CONCRETE ROADS 105 

Joints and cracks can be successfully treated by thoroughly cleaning 
them and filling when dry, and preferably during warm weather, with hot 
tar, then covering with dry sand or screenings. The tar should be per- 
mitted to lap over the spalled edges of the crack, but not to exceed 1 inch. 
The most desirable covering is clean, coarse sand or cleans creenings of stone, 
slag or gravel, that will pass a ^-inch circular opening, and be retained 
on a ^-inch mesh screen. The tar should be poured when hot enough to 
run readily into the crevices of the pavement (about 200° to 250** F.). 
It is believed that no large excess of the tar should be used as the frequent 
use of such an excess might eventually build up an elevation on the sur- 
face which would be objectionable to traflBc. The covering of screenings 
or sand should be put on immediately after pouring the tar so that while 
in the liquid state it will unite with the screenings or sand in sufficient 
degree to prevent the tar from sticking to wheels of vehicles or melting 
during hot periods and running from the cracks. 

The use of a mastic consistmg of a mixture of hot tar and sand, in place 
of pure tar, for filling the cracks and joints, gives promise of excellent 
results; but perhaps it is too soon to give definite specifications for this 
mixture. The filling of the larger and more open cracks or joints with 
the mastic, and the use of the pure tar for filling the minor openings in 
the pavement and such as are made necessary by settlement after the 
joints have been origmally filled with the mastic, may be found to be most 
satisfactory. 

A pouring can with a round or vertical spout is very satisfactory for 
pouring tar in filling cracks and joints. Inasmuch as it is desired that 
the tar shall lap over the edges of the crack or joint, the use of a conical 
pouring can would be of doubtful economy. 

Small holes and shallow depressions can be successfully treated as fol- 
lows: Clean surface thoroughly. Where the surface is disintegrated it 
should first be thoroughly swept with a steel broom in order to remove 
all loose spalls or foreign matter; afterward, the dust must be removed 
by sweeping with a rattan or house broom. The hot tar is then applied 
to the dry concrete and rubbed well with a squeegee or stiff broom to se- 
cure a good bond to the surface of the concrete. The tar is then covered 
with coarse sand or screenings (^ to ^ inch) of stone, slag or gravel. The 
amount of tar used will vary from ^ to 1 gallon per square yard, depending 
upon the depth of the depression to be filled. When more than \ gallon 
per square yard is used, it should be applied in two coats and the excess 
screenings swept off before the second coat is applied. The more tar 
that is applied to the surface, the more desirable it is to have the coarser 
material for a covering. In filling small holes the application of the tar 
in two layers would, of course be unnecessary. 

To repair larger holes and deeper depressions than those discussed 
above : Thoroughly clean and paint the surface with tar. Fill the hole 
or depression with broken stone, preferably of such size that they will 
not exceed in diameter one-half the depth of the depression to be filled 
nor exceed in size stone suitable for an ordinary tar macadam. The stone 
should be levelled off and compacted as well as may be by tamping 
or rolling so as to conform to the true surface of the road. The voids are 
then filled with the hot tar and screenings applied to the surface, which 
is again compacted and treated as in building a tar macadam. 

The use of a cold mix consisting of clean, hard stone chips coated with 
a coal tar cutback, for filling such holes and depressions, as described 
under the above paragraph, has been followed to some extent with very 
promising results. The stone chips are first thoroughly coated with the 
cold tar preparation by turning with shovels after the tar has been 
spray«d upon them, as in mixing ordinary cement concrete. The mixture is 



106 AMERICAN HIGHWAY ASSOCIATION 

then permitted to stand a few days until the lighter oils vaporize from the 
tar, which leaves the stone coated with the heavy tar. The coated chips 
are then well tamped into the hole or depression to be filled, the shallower 
depressions being first painted with the pure tar. Coarse sand or fine 
screenings are then spread over the surface. If the voids appear quite 
open after the coated chips have been thoroughly tamped, a light appli- 
cation of the tar is made to seal up the voids before the surface screenings 
are applied. 

Where the pavement is disintegrated badly or broken clear through so 
as to require rebuilding, it should be cut away with vertical edges. After 
the subgrade is levelled and compacted and the edges and subgrade thor- 
oughly dampened (but the foundation not made muddy), the part cut 
away is replaced with new concrete conforming in quality as nearly as 
possible to the concrete of the surrounding pavement. It is w^ell to coat 
the edges of the old concrete with cement grout. Care should be taken 
that the surface of the new concrete conforms to the surface of the adja- 
cent concrete. The new concrete should be kept well dampened for about 
seven days, and protected from trafiic (ten days in warm weather and 
much longer in cold weather) until thoroughly hardened. If the replace- 
ment is over an excavation the concrete should be properly reinforced. 



STANDARD SPECIFICATIONS FOR PORT- 
LAND CEMENTi 

1. Portland cement is the product obtained by finely pul- 
verizing clinker produced by calcining to incipient fusion, an 
intimate and properly proportioned mixture of argillaceous and 
calcareous materials, with no additions subsequent to calcination 
excepting water and calcined or uncalcined gypsum. 

2. Chemical Properties. — The following limits shall not be 
exceeded: 

Loss on ignition, per cent 4 . 00 

Insoluble residue, per cent 0.85 

Sulfuric anhydride (SO3), per cent 2.00 

Magnesia (MgO), per cent 5.00 

3. Physical Tests. — The specific gravity of cement shall be not 
less than 3.10 (3.07 for white Portland cement). Should the test 
of cement as received fall below this requirement a second test 
may be made upon an ignited sample. The specific gravity test 
will not be made unless specifically ordered. 

4. The residue on a standard No. 200 sieve shall not exceed 22 
per cent by weight. 

5. A pat of neat cement shall remain firm and hard, and show 
no signs of distortion, cracking, checking, or disintegration in 
the steam test for soundness. 

6. The cement shall not develop initial set in less than forty- 
five minutes when the Vicat needle is used or sixty minutes when 
the Gillmore needle is used. Final set shall be attained within 
ten hours. 

7. The average tensile strength in pounds per square inch of 
not less than three standard mortar briquettes composed of one 
part cement and three parts standard sand, by weight, shall be 
equal to or higher than the following: 

^ Adopted by the American Society for Testing Materials in 1904 and re- 
vised in 1908, 1909 and 1916. These specifications are the result of several 
years' work of a special committee representing a United States Govern- 
ment Departmental Committee, the Board of Direction of the American 
Society of Civil Engineers and Committee C-1 on Cement of the American 
Society for Testing Materials, in cooperation with Committee C-1. The 
specifications as here printed are but the first part of the Society's "Stand- 
ard Specifications and Tests for Portland Cement," as officially published. 

107 



108 AMEKICAN HIGHWAY ASSOCIATION 



AGE AT 
TEST 


STORAGE OF BRIQUETTES 


TEN8ILB 
STRENGTH 


day» 

7 


1 day in moist air, 6 days in water 


lb. per aq.xH. 

200 


28 


1 day in moist air, 27 days in water 


300 









8. The average tensile strength of standard mortar at twenty- 
eight days shall be higher than the strength at seven days. 

9. Packages, Marking and Storage. — The cement shall be de- 
livered in suitable bags or barrels with the brand and name of 
the manufacturer plainly marked thereon, unless shipped in 
bulk. A bag shall contain 94 pounds net. A barrel shall con- 
tain 376 pounds net. 

10. The cement shall be stored in such a manner as to permit 
easy access for proper inspection and identification of each ship- 
ment, and in a suitable weather-tight building which will protect 
the cement from dampness. 

11. Inspection. — Every facihty shall be provided the purchaser 
for careful sampling and inspection at either the mill or at the 
site of the work, as may be specified by the purchaser. At least 
ten days from the time of sampling shall be allowed for the com- 
pletion of the 7-day test, and at least 31 days shall be allowed for 
the completion of the 28-day test. The cement shall be tested 
in accordance with the methods hereinafter prescribed. The 
28-day test shall be waived only when specifically ordered. 

12. Rejection. — The cement may be rejected if it fails to meet 
any of the requirements of these specifications. 

13. Cement shall not be rejected on account of failure to meet 
the fineness requirement if upon retest after drying at 100°C. 
for one hour it meets this requirement. 

14. Cement failing to meet the test for soundness in steam 
may be accepted if it passes a retest using a new sample at any 
time within 28 days thereafter. 

15. Packages varymg more than 5 per cent from the specified 
weight may be rejected; and if the average weight of packages 
in any shipment, as shown by weighing 50 packages taken at 
random, is less than that specified, the entire shipment may be 
rejected. 



PETROLEUM AND RESIDUUMS' 

A large part of the materials used as dust preventives and 
binders to hold together the mineral constituents of roads are 
obtained from petroleum. Petrolemn is a term which covers 
mineral oils of a great variety of characteristics, all alike in being 
composed of a great variety of complex chemical compounds 
called hydrocarbons, of which there is a very large number. 
The investigation of the properties of these hydrocarbons and 
their derivatives requires a knowledge of organic chemistry which 
few roadbuilders possess, and because some of them have at- 
tempted to tread the veritable mazes of this extremely compli- 
cated domain of chemistry, no little confusion has arisen. The 
main facts regarding petroleum and the other hydrocarbons used 
in roadbuilding are definitely known, but the details of any group 
of these compounds are best left for the chemical specialist, who 
is making steady progress in his researches concerning them. 

Paraffin and Asphaltic Oils 

The roadbuilder's interest in petroleum is largely in its base, 
a term used to designate a part of oil left after distilhng off the 
more volatile portions. The base is sometimes made up of com- 
pounds of the paraffin group or series, as chemists term such 
allied compounds. Marsh gas is a member of the paraffin series, 
and its least complex representative. A few other members are 
gases but most of them are liquids or soHds, and their number is 
legion. The base of other petroleums is made up of compounds 
called polycyclic polymethylenes by the chemist, and as these 
compounds occur in native asphalts such a base is called asphaltic. 
The base of other petroleums is made up of both paraffin and 
asphaltic compounds and such petroleums are called semi- 
asphaltic. 

The gaseous hydrocarbons are of no interest to the roadbuilder. 
The hquid and solid hydrocarbons are what determine the value 
of petroleum for his purposes. The hquid and solid paraffins are 
greasy materials without binding properties, while the asphaltic 
materials are sticky. Consequently the roadbuilding value of 
petroleum depends upon the asphaltic compounds in its base. 

^ Revised by Pr6vost Hubbard, chief of road materials tests and re- 
oearch, United States Office of Public Roads. 

109 



110 AMERICAN HIGHWAY ASSOCIATION 

Paraffin oils have been used successfully as dust preventives 
when sprinkled in small quantities on a clean road, but if used in 
large quantities they form a greasy, dirty surface and seem to 
lubricate the pieces of stone in the road, which becomes rutted 
rapidly. 

Petroleum is obtained from many districts, which are called 
fields in the industry. The leading fields which supply or have 
supplied materials for roadbuilding in the United States are 
discribed substantially as follows by John D. Northrop in Mineral 
Resources of the United States, 1915: 

1. The Appalachian field embraces all oil pools east of central 
Ohio and north of central Alabama, including those of New York, 
Pennsylvania, West Virginia, southeastern Ohio, Kentucky, 
Tennessee, and northern Alabama. The oils of the Appalachian 
field are in the main of paraffin base, free from asphalt and prac- 
tically free from sulphur, and they yield by ordinary refining 
methods high percentages of gasoline and illuminating oils — the 
products in greatest demand. 

2. The Lima-Indiana field embraces all areas of oil production 
in the northwestern part of Ohio and in Indiana. The petroleum 
of the Lima-Indiana field contains some asphalt, though con- 
sisting chiefly of paraffin hydrocarbons with sulphur compounds. 

3. The Illinois field lies in the southeastern, south-central and 
western parts of the State, comprising about 16 counties. lUinois 
oils contain varying proportions of both asphalt and paraffin 
and differ considerably as to specific gravity and distillation 
products. Sulphur is generally present. 

For commercial purposes it is customary to group under the 
title ''Mid-Continent field" the areas of oil production in Kansas, 
Oklahoma, northern and central Texas, and northern Louisiana. 
Mid-continent oils vary in composition within wide limits, rang- 
ing from asphaltic oils poor in gasoline and illuminants, to oils 
in which the asphalt content is neghgible and the paraffin con- 
tent relatively high and which yield correspondingly high per- 
centages of the fighter products on distillation. Sulphur is pres- 
ent in varying quantities in the lower grade oils. 

5. The term ''Gulf field" includes that portion of the gulf 
coastal plain of Texas and Louisiana in which petroleum is found 
in domes, associated with rock salt and gypsum. Oils from the 
Gulf field are characterized by relatively high percentages of 
asphalt and low percentages of the lighter gravity distillation 
products. Considerable sulphur is present, much of which, how- 
ever, is in the form of sulphureted hydrogen and is easily removed 
by steam before refining or utilizing the oil as fuel. 

6. The CaHfornia field is mainly located in Kern, Fresno, 
Orange, Santa Barbara and Los Angeles Counties. The Call- 



PETROLEUM AND RESIDUUM8 



111 



fornia oils are generally characterized by much asphalt and little 
or no paraffin and by small proportions of sulphur. The chief 
products are fuel oils, lamp oils, lubricants, and oil asphalt. 

Oils from Wyoming and Colorado are in the main of paraffin 
base, suitable for refining by ordinary methods. Heavy asphaltic 
oils are also obtained in certain of the Wyoming fields. 

7. Mexican field. This extends along the Gulf of Mexico from 
the vicinity of Tampico to the vicinity of Tuxpan, and produces 
asphaltic and semi-asphaltic petroleum. 

8. Trinidad field. A large amount of asphaltic petroleum is 
produced on the island of Trinidad. 

Clifford Richardson gives the following explanation of the rela- 
tion between this petroleum and Trinidad asphalt: 

Rising from the sands in which it occurs and coming in contact with the 
colloidal clay forming a portion of the mud existing below the crater or 
depression which holds the asphalt, it is emulsified with it and converted 
into the material which we recognize as Trinidad lake asphalt. 

Refining Petroleum 

Crude asphaltic petroleum has been used as a dust preventive 
and as a binder, but generally the petroleum is refined to obtain 
a number of valuable materials occurring in it. The crude oil 
is first allowed to settle in tanks in which the mineral matter 



Petroleum Marketed in the United States in 1915 hy Fields 
(John D. Northrop, in Mineral Resources of the United States, 1915) 



Appalachian 

Lima-Indiana 

Illinois 

Mid-continent 

Gulf 

California 

Colorado and Wyoming 
Other fields 



QUANTITY (bar- 
bels OF 42 gal- 
lons) 



22,860,048 

4,269,591 

19,041,695 

123,295,867 

20,577,103 

86,591,535 

4,454,000 

14,265* 



281,104,104 



VALUE 



$35,468,973 

4,114, 228 

18,655,850 

72,437,701 

9,802,901 

36,558,439 

2,400,503 

24,295* 



$179,462,890 



AVBRAQE PRICB 
PER BARREL 



51.552 
0.964 
0.980 
0.588 
0.476 
0.422 
0.539 
1.703 



$0,638 



* Includes Alaska, Michigan, and Missouri. 

Note : The Barber Asphalt Company reports that the importation of 
crude petroleum from Trinidad has been as follows: 1914, 140,438 barrels; 
1915, 330,022 barrels; 1916, 372, uOO barrels. The imports of crude petro- 
leum from Mexico are reported by John D. Northrop as follows: 1914, 
16,245,975; 1915, 17,478,472 barrels. 

A preliminary estimate by J. D. Northrop of the 1916 production in the 
United States is 292,300,000 barrels. 



112 



AMERICAN HIGHWAY ASSOCIATION 



Degrees Baum^, Specific Gravities, Weights in Pounds per Gallon and Volume 
in Gallons per Pound of Petroleum at 60°F. 

(From "United States Standard Tables for Petroleum Oils," United States 

Bureau of Standards) 



D EQRBES 


SPECIFIC 


POUNDS PER 


GALLONS 


DEGREES 


SPECIFIC 


POUNDS PER 


GALLONS 


BAUM^ 


GRAVITY 


GALLON 


PER POUND 


BAVUt 


GRAVITY 


GALLON 


PER POUND 


10.0 


1.0000 


8.328 


0.1201 


19.6 


0.9358 


7.793 


0.1283 


10.2 


0.9986 


8.317 


0.1202 


19.8 


0.9346 


7.783 


0.1285 


10.4 


0.9972 


8.305 


0.1204 


20.0 


0.9333 


7.772 


0.1287 


10.6 


0.9957 


8.293 


0.1206 


20.2 


0.9321 


7.762 


0.1288 


10.8 


0.9943 


8.281 


0.1208 


20.4 


0.9309 


7.752 


0.1290 


11.0 


0.9929 


8.269 


0.1209 


20.6 


0.9296 


7.742 


0.1292 


11.2 


0.9915 


8.258 


0.1211 


20.8 


0.9284 


7.731 


0.1293 


11.4 


0.9901 


8.246 


0.1213 


21.0 


0.9272 


7.721 


0.1295 


11.6 


0.9887 


8.234 


0.1214 


21.2 


0.9259 


7.711 


0.1297 


11.8 


0.9873 


8.223 


0.1216 


21.4 


0.9247 


7.701 


0.1299 


12.0 


0.9859 


8.211 


0.1218 


21.6 


0.9235 


7.690 


0.1300 


12.2 


0.9845 


8.199 


0.1220 


21.8 


0.9223 


7.680 


0.1302 


12.4 


0.9831 


8.188 


0.1221 


22.0 


0.9211 


7.670 


0.1304 


12.6 


0.9818 


8.176 


0.1223 


22.2 


0.9198 


7.660 


0.1305 


12.8 


0.9804 


8.165 


0.1225 


22.4 


0.9186 


7.650 


0.1307 


13.0 


0.9790 


8.153 


0.1227 


22.6 


0.9174 


7.640 


0.1309 


13.2 


0.9777 


8.142 


0.1228 


22.8 


0.9162 


7.630 


0.1311 


13.4 


0.9763 


8.131 


0.1230 


23.0 


0.9150 


7.620 


0.1313 


13.6 


0.9749 


8.119 


0.1232 


23.2 


0.9138 


7.610 


0.1314 


13.8 


0.9736 


8.108 


0.1233 


23.4 


0.9126 


7.600 


0.1316 


14.0 


0.9722 


8.096 


0.1235 


23.6 


0.9115 


7.590 


0.1318 


14.2 


0.9709 


8.086 


0.1237 


23.8 


0.9103 


7.580 


0.1319 


14.4 


0.9695 


8.074 


0.1239 


24.0 


0.9091 


7.570 


0.1321 


14.6 


0.9682 


8.063 


0.1240 


24.2 


0.9079 


7.561 


0.1323 


14.8 


0.9669 


8.052 


0.1242 


24.4 


0.9067 


7.551 


0.1324 


15.0 


0.9655 


8.041 


0.1244 


24.6 


0.9056 


7.541 


0.1326 


15.2 


0.9642 


8.030 


0.1245 


24.8 


0.9044 


7.531 


0.1328 


15.4 


0.9629 


8.019 


0.1247 


25.0 


0.9032 


7.522 


0.1330 


15.6 


0.9615 


8.007 


0.1249 


25.2 


0.9021 


7.512 


0.1331 


15.8 


0.9602 


7.997 


0.1250 


25.4 


0.9009 


7.502 


0.1333 


16.0 


0.9589 


7.986 


0.1252 


25.6 


0.8997 


7.493 


0.1335 


16.2 


0.9576 


7.975 


0.1254 


25.8 


0.8986 


7.483 


0.1336 


16.4 


0.9563 


7.964 


0.1256 


26.0 


0.8974 


7.473 


0.1338 


16.6 


0.9550 


7.953 


0.1257 


26.2 


0.8963 


7.464 


0.1340 


16.8 


0.9537 


7.942 


0.1259 


26.4 


0.8951 


7.454 


0.1342 


17.0 


0.9524 


7.931 


0.1261 


26.6 


0.8940 


7.445 


0.1343 


17.2 


0.9511 


7.921 


0.1262 


26.8 


0.8929 


7.435 


0.1345 


17.4 


0.9498 


7.910 


0.1264 


27.0 


0.8917 


7.425 


0.1347 


17.6 


0.9485 


7.899 


0.1266 


27.2 


0.8906 


7.416 


0.1348 


17.8 


0.9472 


7.888 


0.1268 


27.4 


0.8895 


7.407 


0.1350 


18.0 


0.9459 


7.877 


0.1270 


27.6 


0.8883 


7.397 


0.1352 


18.2 


0.9447 


7.867 


0.1271 


27.8 


0.8872 


7.388 


0.1354 


18.4 


0.9434 


7.856 


0.1273 


28.0 


0.8861 


7.378 


0.1355 


18.6 


0.9421 


7.846 


0.1275 


28.2 


0.8850 


7.369 


0.1357 


18.8 


0.9409 


7.835 


0.1276 


28.4 


0.8838 


7.360 


0.1359 


19.0 


0.9396 


7.825 


0.1278 


28.6 


0.8827 


7.351 


0.1360 


19.2 


0.9383 


7.814 


0.1280 


28.8 


0.8816 


7.341 


0.1362 


19.4 


0.9371 


7.804 


0.1281 


29.0 


0.8805 


7.332 


0.1364 



Note: Tables for oils of greater specific gravity than 1.000 and of the 
comparative volumes of oils at 60° and other temperatures are given on 
pages 129 and 131. 



PETROLEUM AND RESIDUUM8 113 

and water are separated from the oil. The latter is drawn off 
into cylindrical stills set horizontally in brickwork like boilers. 
There is a furnace below the still, and the latter contains steam 
coils and sometimes steam jets at the bottom of the stills. The 
heating by means of the furnace and the steam coils and jets 
should be conducted very carefully, if the final products are to 
be used for road work, and careless heating has resulted in very 
undesirable materials being sold for highway purposes. The 
vapors from the stills are removed to condensers and liquefied. 

The distillate that is obtained until the temperature reaches 
about 300°F. and the specific gravity of the product is about 0.73 
is refined to furnish gasoline and naphtha. While the tempera- 
ture is increased from 300° to 575°F., the specific gravity of the 
distillate increases to about 0.82, and the oil produced during 
this stage is treated to supply kerosene. If it is desirable to pro- 
duce as much kerosene as possible the furnace is heated and the 
sides of the still kept as cool as possible, so that some of the 
heavy vapor driven off in the bottom of the still will condense 
in the top and fall back into the much hotter material at the 
bottom, ^'cracking" these heavy vapors into lighter compounds. 
One result of such cracking is often the Uberation of free carbon, 
which settles into the material in the bottom of the still. As- 
phaltic oils can be cracked at a lower temperature than paraffin 
oils. 

If road oils for surface treatment are desired, the distilling 
process is stopped after the light distillates are driven off. The 
thick oil left in the still is called the residuum, and some people 
look upon it as a by-product and the name ''residuum" as having 
a somewhat derogatory signification. As a matter of fact the 
residuum obtained in distilling some petroleums is by far the most 
important product obtained from them. Some Californian and 
Mexican oils contain such a large amount of asphaltic compounds 
and so little light oils that by stopping the refining process when 
the residuum has the consistency desired for some classes of 
paving materials, it is unnecessary to add any other bitumen to 
fit it for use. 

In the patented Trumbull process, the oil is heated and then 
allowed to flow down the inner surface of a large vertical heated 
cylinder. The vapors are drawn from the top of the cyhnder 
and the asphaltic residuum is collected at the bottom. The 
temperatures used and the rate at which the crude oil is fed to 
the top of the cyhnder fix the consistency of the residuum. 

One of the earhest attempts to improve the process of refining 
petroleum so as to yield the maximum quantity of products useful 
for paving was made by Dubbs. By adding sulphur to the 
residuum while it was at a high temperature he produced mate- 



114 AMERICAN HIGHWAY ASSOCIATION 

rials which have been widely used as fluxes. About the same 
time Byerly found that by blowing air through the heated re- 
siduum asphaltic products were obtained, the oxygen performing 
the same function as the sulphur used in the Dubbs process. 
Some of these blown-oil products have been used as fluxes and 
others have been used for a great variety of purposes. Some 
asphaltic oils furnish a residuum which does not require blowing 
to obtain road material but this treatment is generally employed 
with semi-asphaltic oils when such a product is desired. Appar- 
ently the hydrocarbons of the paraffin series are little affected by 
the blowing process, which affects compounds of other series. 

Meaning of Analyses. — The characteristics of the residuums 
from various oils are given in the accompanying table. The fol- 
lowing notes explain the significance of the information in the 
table, and are abridged from Provost Hubbard's Dust Preventives 
and Road Binders. 

Specific Gravity.— The mark "25725°C." indicates that the 
determination was made at 25°C. (77°F.) and the result expressed 
in comparison with water at the same temperature. The test 
is mainly useful in identifying the material, but also gives a rough 
indication of the amount of heavy hydrocarbons which give 
body to the material. Material having a specific gravity exceed- 
ing 0.93 or 0.94 should be heated before use. 

Flash Point. — This test is of value as differentiating between 
the heavy crude oils and cut-back^ products, and the fluid re- 
siduums. It also shows the point to which a refined oil has been 
distilled and whether it is advisable to heat the material before 
apphcation. 

Loss at 160°C. — The loss in weight is an indication of the rela- 
tive losses by volatilization of different road oils in actual service. 
It is an empirical test, like the rattler test for paving bricks. The 
residue should be sticky. If it is desirable for the material to 
maintain its consistency after application, it should show a low 
loss. If the material is applied by a method which requires more 
or less fluidity, a high loss is permissible, in order that the mate- 
rial may rapidly attain the desired consistency in the road, 
although a high loss is not necessary in the case of dust preven- 
tives. The loss is now usually determined at 163°C. 

Loss at 205°C. — The purpose of this test is to show the effect 
of a high temperature as compared with 160° or 163°. It is not 
often made. 

Bitumen Soluble in CS2. — The solubility of the bitumen itself 
is independent of its character and consistency, so the amount 
and character of insoluble material is of most interest. 

^ A cut-back product is one made by fluxing a dense asphalt with a 
light oil. 



PETROLEUM AND RESIDUUMS 



115 





03 




^ 




-O 




:3 


CO 


W 


3 


^-3 

o 


i~~> 


> 


o 


VU 


s^ 


(-( 


« 


Ph 


a. 


>> 


■fcj 


^ 


s 




^o 


&5 


^ 


^ 


"S, 




•<-» 

Q 


K 

•^ 






"^ 


O 


CO 


ti; 


s 


•Tf 


S 


ss 


s 


c-i 


CO 


CO 


V/ 


;>> 


Q^ 






S 



^cu 



•5 


.^^ 


V 


09 


•<?i 


» 




Q 




a 


I- 


o 


Oh 


t-l 




>> 








a 








55 




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^ o 5 



w w o 

OQ P^ I-] 

n 



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b O H 

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a 



ida 

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^ > 00 

w ^ w 
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tr> 



oo 

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o o c^ i; coin 

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116 AMERICAN HIGHWAY ASSOCIATION 

Inorganic Matter. — This indicates in some cases the nature of 
the dense bitumen. 

Insoluble Organic Matter. — ^This affords an indication of 
whether oil has been distilled destructively. 

Bitumen Insoluble in 88°B. Naphtha. — ^The hydrocarbons in- 
soluble in paraflBn naphtha are termed '^asphaltenes'^ and those 
which are soluble "malthenes." The former tend to give body 
and consistency and the latter contribute adhesive properties to 
a road material. Blown oils contain very high amounts of insol- 
uble hydrocarbons, sometimes as much as 25 to 30 per cent. The 
character of the bitumen dissolved in naphtha, after the solvent 
has evaporated, is instructive, for a sticky residue indicates better 
road building quaUties in the original material than that which 
is greasy. 

Soluble Bitumen Removed by H2SO4 and Saturated Hydro- 
carbons in Total Bitumen. — These tests are mainly of value as 
indicating the source of the material imder examination. CUfford 
Richardson gives the following explanation of the significance of 
the tests in The Modem Asphalt Pavement: 

Hydrocarbons in general are divided into those which are saturated 
and those which are unsaturated, the former being stable and the latter 
reactive and very susceptible to change, combining with or being con- 
verted into other hydrocarbons by the action of sulphuric acid and other 
reagents. The saturated can be separated from the unsaturated hydro- 
carbons by strong sulphuric acid, and this will be found to be a very impor- 
tant means of differentiating the oils and the solid bitumens among them- 
selves, by determining the relative proportions of these two classes of 
hydrocarbons which they contain. 

SoHd Paraffin. — This test confirms the information obtained 
from an inspection of the residue after the test of the loss at 
160°C. The heavy hquid hydrocarbons of the paraffin series are 
probably more detrimental in road oils than are the solid parafl^s. 

Fixed Carbon. — Fixed carbon is the coke resulting from the 
ignition of the bitumen in the absence of oxygen. 

Fluxes 

Fluxes are petroleum products which are mixed with harder 
bituminous materials to soften them to any desired consistency. 
Petroleum with a parafl&n base furnished the first flux used in 
the asphalt paving industry. 

Asphaltic or semi-asphaltic flux is the residuum left on distilling 
petroleum having an asphaltic or semi-asphaltic base to a point 
where the residuum is a dense liquid when cool but any further 
distillation will produce a solid residuum when cold. It is char- 
acterized by a relatively low amount of saturated hydrocarbons. 
While it resembles natural maltha in some respects, it differs in 
remaining soft after heating to 400°F., most malthas becoming 
hard pitches after such treatment. 



ASPHALT AND NATIVE SOLID BITUMENS^ 

The following definition of "asphalt" has been adopted by the 
American Society for Testing Materials: 

Solid or semi-solid native bitumens, solid or semi-solid' bitumens 
obtained by refining petroleum, or solid or semi-solid bitumens which are 
combinations of the bitumens mentioned with petroleums or derivatives 
thereof, which melt upon the application of heat and which consist of a 
mixture of hydrocarbons and their derivatives of complex structure, 
largely cyclic and bridge compounds. 

This definition is dependent upon the same society's definition 
of "bitumens," which is: 

Mixtures of native or pyrogenous hydrocarbons and their non-metallic 
derivatives, which may be gases, liquids, viscous liquids, or solids, and 
which are soluble in carbon disulphide. 

These definitions were prepared after numerous conferences of 
road engineers and producers of materials, and while adopted by 
the society are not accepted by all specialists. 

The following definitions are given by CUfford Richardson in 
The Modern Asphalt Pavement: 

Native bitumens consist of a mixture of native hydrocarbons and their 
derivatives, which may be gaseous, liquid, a viscous liquid or solid, but, 
if solid, melting more or less readily on the application of heat, and solu- 
ble in turpentine, chloroform, bisulphide of carbon, similar solvents, and 
in the malthas or heavy asphaltic oils. Natural gas, petroleum, maltha, 
asphalt, grahamite, gilsonite, ozocerite, etc., are bitumens. Coal, lignite, 
wurtzelite, albertite, so-called indurated asphalts, are not bitumens, be- 
cause they are not soluble to any extent in the usual solvents for bitumen, 
nor do they melt at comparatively low temperatures nor dissolve in heavy 
asphaltic oils. These substances, however, on destructive distillation 

^ Revised by Provost Hubbard, chief of road materials tests and re- 
search, United States Office of Public Roads. 

' Solid bituminous materials are those having a penetration at 25°C. 
(77°F.) under a load of 100 grams applied for five seconds, of not more than 
10. The significance of "penetration" is explained on page 121. 

Semi-solid bituminous materials are those having a penetration at 25°C. 
(77° F.) under a load of 100 grams applied for five seconds, of more than 
10 and a penetration under a load of 50 grams applied for 1 second of not 
more than 350. 

Liquid bituminous materials are those having a penetration at 25°C. 
(77° F).) under a load of 60 grams applied for one second or more than 
350., 

117 



118 AMERICAN HIGHWAY ASSOCIATION 

give rise to products which are similar to natural bitumens, and they have 
been on this account defined by T. Sterry Hunt as "pyro-bitumens," 
which differentiates them very plainly from the true bitumens." 

Asphalt is a term used industrially to cover all the solid native bitu- 
mens used in the paving industry and specifically to include only such as 
melt on the application of heat, at about the temperature of boiling water, 
are equally soluble in carbon bisulphide and carbon tetrachloride and to 
a large extent in 88° naphtha, those hydrocarbons soluble in naphtha 
consisting to a very considerable degree of saturated hydrocarbons, yield- 
ing about 15 per cent of fixed carbon and containing a high percentage of 
sulphur. Under this definition it can be seen that grahamite is not an 
asphalt, since it is not largely soluble in naphtha and yields a very high 
percentage of fixed carbon on ignition. It is also less soluble in carbon 
tetrachloride than in carbon bisulphide. Gilsonite is not an asphalt, 
since the saturated hydrocarbons contained in the naphtha solution are 
very small in amount and quite different in character from those found 
in asphalt. 

Roadbuilders use the term "natural asphalts" to designate 
the native solid or semi-solid asphalts, and "oil asphalts" to desig- 
nate the corresponding materials prepared from petroleum or 
maltha. Some producers of oil asphalts object to the term on 
the ground that the material obtained by distilling away the 
lighter parts of asphaltic petroleum is as "natural" as that 
obtained by refining native asphalts. By "rock asphalt" is 
meant sandstone and limestone impregnated with asphalt or 
maltha. "Asphaltic sands" are mixtures of asphalt or maltha 
and sand, the latter in loose grains which fall apart when the 
bitumen is extracted; many of them are called rock asphalts 
because in their natural condition the maltha cements them into 
a rock-like mass. 

The sources of the asphalts used in the United States are given 
in the accompanying table. The quantities of materials there 
stated were not all used for road and street purposes, as there are 
many other uses to which some of them are put. 

Trinidad Asphalt. — Trinidad asphalt comes from the island of 
that name. The main source is on La Brea Point, about 28 miles 
from Port of Spain, the chief town. Here there is a circular pitch 
lake of nearly 115 acres extent, between which and the sea are 
other pitch deposits more or less mixed with sand. The former 
furnishes the "lake asphalt" and the latter the "land asphalt" 
of the paving industry. 

The material in the lake is described by CHfford Richardson 
as an emulsion of water, gas, bitumen, fine sand and clay. It is 
in constarit motion owing to the evolution of gas, and for this 
reason, whenever a hole is dug in the surface, whether deep or 
shallow, it rapidly fills up and the surface resumes its original 
level after a short time. Although soft it can be readily flaked 
out with picks in large conchoidal masses weighing 50 to 75 



ASPHALT AND NATIVE SOLID BITUMENS 



119 



pounds. It is honey-combed with gas cavities and resembles a 
Swiss cheese in structure. It is of uniform composition, as 
follows: Water and gas volatiHzed at 100°C., 29 per cent; bitumen 
soluble in cold carbon disulphide, 39 per cent; bitumen absorbed 

American Production and Importation of Asphaltic Materials, 1916 

(Compiled from report by John D. Northrop in Mineral Resources of the 

United States, 1915. Output stated in tons of 2000 pounds, except 

in case of imports, which are in tons of 2240 pounds) 



American bituminous rock .... 
Wurtzelite (elaterite), gilsonite 
Grahamite 



Total American natural bitu- 
minous material 



American road oils and fluxes , 
American oil asphalts and 
pitches 



Total American road oils, as- 
phalts, etc 



Mexican road oils and fluxes* 

Mexican oil asphalts and 

pitches* 



Total Mexican road oils, as- 
phalts, etc* 



Imports of asphalt 

Trinidadf 

Bermudez 

Cuba 

Barbados 

Mexico 

Switzerland 

Italy 

France 

England 

Germany 



1915 



Tons 



44,329 
20,559 
10,863 



75,751 
417,859 
246,644 



664,503 
174,854 
213,464 



388,318 



92,107 

28,659 

391 

64 

56 

200 

492 



774 
658 



Value 



$157,083 

275,252 

94,155 



526,490 
2,392,576 
2,323,007 



4,715,583 
1,325,201 
2,405,235 



3,730,436 



498,900 
144,595 
9,243 
6,426 
755 
1,637 
3,438 



9,801 
4,854 



1914 



Tons 



51,071 

19,148 
9,669 



79,888 
171,447 

189,408 



360,855t 

111,058 

202,729 



313,787 



61,708 

58,755 

458 

71 

140 

620 

247 

100 

628 

1,354 



Value 



$162,622 

405,966 

73,535 



642,123 



3,016,969 



4,131,153 



334,635 

295,765 

11,407 

6,592 

2,048 

3,706 

1,477 

1,317 

6,269 

10,856 



* Refined in the United States from imported Mexican petroleum, 
t There are discrepancies in the figures in the report. 

by mineral matter, 0.3 per cent; mineral matter, 27.2 per cent; 
water of hydration in clay and silicates, 4.3 per cent. 

Trinidad land asphalt reached the places where it is found 
either by overflowing from the lake or by intrusion into the soil 
from the same subterranean source that supplies the lake asphalt. 



120 



AMERICAN HIGHWAY ASSOCIATION 



Its character is much affected by the effect of the weathering to 
which it has been subjected. CHfford Richardson states that 
refined land asphalt of good quality differs from the lake supply 
by its higher specific gravity due to the larger amount of mineral 
matter it contains, by a higher softening or melting point, and 
a somewhat lower percentage of bitumen and, in consequence of 
these facts, a much greater hardness at all temperatures. Land 
asphalt requires much more paraflan flux than lake asphalt, and 
asphaltic oil fluxes offer certain advantages over paraffin fluxes 
for use with land asphalt. 



Composition of Refined Trinidad and Bermudez Asphalts 
(Clifford Richardson) 



Specific gravity at 77°F. (25°C.) 

Streak 

Lustre 

Structure 

Fracture 



Hardness 

Melts 

Penetration at 77°F. (25°C.) 

Loss at 325°F. (163°C.), 7 hours 

Character of residue 

Loss at 400°F. (205°C.) 7 hours 

Character of residue 

Bitumen soluble in CS2 

Bitumen retained by mineral matter 

Mineral matter 

Water of hydration 

Vegetable matter 

Bitumen soluble in 88° naphthp; 

Percentage of total bitumen which above is 

Soluble bitumen removed by H2SO4 

Saturated hydrocarbons in total bitumen. . 

Pure bitumen soluble in C CI4 

Fixed carbon 



TKINIDAD 



1.40 
Blue black 
Dull 
Homogeneous 
Semi-con- 
choidal 
2 
235°F.(113°C.) 
4 

1.1% 
Smooth 

4.0% 
Blistered 

56.5% 

0.3% 
38.5% 

4.2% 



35.6% 
63.1% 
61.3% 

24.4% 

100.0% 

10.8% 



BBRMtTDEZ 



1.08 
Black 
Bright 
Uniform 
Semi-con- 
choidal 
Soft 
183°F. (84°C. 
20 
3% 
Smooth 
8.2% 
Wrinkled 
94.4% 



3.6% 



2.0% 

62.2% 
65.4% 
62.4% 
24.4% 
99.5% 
13.4% 



Bermudez Asphalt. — Bermudez asphalt comes from a pitch lake 
in Venezuela about 30 miles from the coast in an air line. The 
lake is about Ih miles long, 1 mile wide, of irregular shape and 
covers about 900 acres. It is covered with a crust from a few 
inches to 2 feet thick, having some grass and shrubs, with a few 
palms, and the pitch is visible on the surface in but few places. 
It is very wet, so that excavations fill with water and it is diffi- 
cult to excavate the pitch, which has an average depth of 4 feet. 
The deposit is probably formed by the exudation of a large quan- 
tity of soft maltha. The asphalt from the lake varies greatly in 



ASPHALT AND NATIVE SOLID BITUMENS 121 

the amount of water it contains, which fluctuates between 11 
and 46 per cent. This water is not emulsified with the bitumen 
but is adventitious surface water. The material for industrial 
use is selected, and when refined has the composition given in 
the accompanying table, which also gives the composition of refined 
Trinidad asphalt. 

Meaning of Analyses. — The significance of most of the terms 
used in this table are explained in the section on Petroleum. The 
new terms are the following: 

Streak is the color of a rubbed or scratched surface. 

Hardness is stated in terms of Mohr's scale, in which 1 is the 
hardness of talc, 2 that of rock salt, 3 that of calcite, 4 that of 
fluorite, etc. When a bitumen is softer than I on this scale its 
hardness is stated by its behavior in a penetration test, explained 
below. 

Melting point is determined by an arbitrary test, because 
bituminous materials are made up of a mixture of hydrocarbons 
and their derivatives and can not have a true melting point, such 
as a definite compound possesses. 

Penetration is determined by the distance that a needle of 
specified size loaded with a specified weight will penetrate into a 
sample of the material in a specified time. Usually a No. 2 
needle loaded so that the total weight is 100 grams and a time 
period of 5 seconds is employed, but a 50-gram weight and a 
1-second time period are used with liquid bitumens. Prevost 
Hubbard makes the following statement regarding this test: 

The penetration test is a convenient one to employ for identification 
and control, and is often indicative of the value of an oil or asphalt product 
for construction work. While the test for bituminous road materials is 
made in the same manner as in asphalt paving work, the standards for 
road purposes are somewhat different. No oil product should be employed 
in macadam construction with a penetration higher than 25 mm, when 
tested at 25''C. with a No. 2 needle for five seconds under a weight of 100 
grams, unless it possesses the property of hardening considerably when 
subjected to the volatilization test. On the other hand, it is rarely neces- 
sary to require a penetration as high as that for asphaltic cement used in 
the topping of an asphalt pavement, for the reason that the upper course 
of a macadam road has much greater inherent stability than the sand 
course of the asphalt pavement. A penetration of from 10 to 15 mm. is 
usually considered sufficient for road work. If a material having a much 
lower penetration is selected, its susceptibility to temperature changes 
will have to be considered. 

Organic matter insoluble is a term of uncertain significance 
which has been explained by Chfford Richardson as follows: 

On adding together the percentages of bitumen soluble in carbon disul- 
phide and of inorganic matter obtained on ignition, the sum will seldom 
amount to 100.0. The difference has been considered for many years as 



122 AMERICAN HIGHWAY ASSOCIATION 

organic matter not bitumen (insoluble). This may be true in exceptional 
cases, but recent investigations have shown that it is not at all so in many 
bitumens. For example, in Trinidad asphalt it has been found to consist 
of the water of combination of the clay which the material contains and 
some inorganic salts which are volatilized on ignition. The amount of 
organic matter is extremely small. In other cases, it may consist to a 
considerable extent of grass and twigs, as in the seepages which have run 
out over sod. On the whole, therefore, it seems desirable not to describe 
it by any definite name, but merely as an undetermined difference. 

Pure bitumen soluble in CCI4 (carbon tetrachloride) is not 
usually determined unless a road oil has been badly cracked or a 
solid bitumen Uke grahamite has been added, so that the per- 
centage of hydrocarbons insoluble in 88° naphtha is high. The 
bitumens insoluble in carbon tetrachloride but soluble in carbon 
bisulphide are called "carbenes." 

Other Asphalts. — Maracaibo asphalt is found on the Limon 
River about 50 miles west of Maracaibo, Venezuela. According 
to Clifford Richardson it is an exudation from maltha springs. 
When carefully refined it contains from 92 to 97 per cent of 
bitumen soft enough to be indented by the finger nail. It con- 
tains a very small percentage of malthenes and has a higher soften- 
ing point than either Trinidad or Bermudez asphalt. 

Cuban asphalts are found in small quantities in many places 
on the island and what little use of them is made in the IJnited 
States is mainly for varnishes. A deposit 18 miles from Havana 
has furnished material used in street pavements. 

Asphaltic materials are found in many places in Mexico, and 
some of them have been developed more or less. What is usually 
known among roadbuilders as Mexican asphalt is prepared from 
the malthas and petroleums obtained mainly from the Tampico 
and Tuxpan district. 

Natural asphalt has been obtained in California at several 
places, but the most noted deposits are no longer worked. 

Refining natural asphalt consists merely in driving off the 
water it contains by heating the material to about 325°F. in 
large tanks containing coils of pipes through which steam is 
passed. In the bottom of the tanks are steam jets which agitate 
the asphalt. The vegetable impurities, if any, are skimmed from 
the top. The refined asphalt is drawn off while it is hquid into 
barrels for shipment. When it is to be used, it is melted with a 
residuum flux. 

Solid Bitumens not Asphalts. — Gilsonite is a hard, brittle bitu- 
men with a reddish brown streak and a conchoidal fracture, 
obtained mainly from Utah and Colorado. It is sold in two 
grades, gilsonite selects and gilsonite seconds, the former being 
the more pure. Gilsonite from different mines varies consider- 
ably, and some of it is of little value for use in paving mixtures. 



ASPHALT AND NATIVE SOLID BITUMENS 



123 



Grahamite is a hard, brittle bitumen with a black streak, 
otherwise resembling gilsonite in appearance. Its softening 
point is very high and not yet definitely determined. It is 
obtained mainly from Oklahoma. 

Properties of Gilsonite and Grahamite 
(Clifford Richardson, The Modern Asphalt Pavement) 



Specific gravity, 78778°F. . . . 

Streak 

Lustre 

Fracture 

Hardness 

Softens 

Flows 

Loss, 325°F., 7 hours 

L9SS, 400°F., 7 hours 

Bitumen soluble in CS2 

Insoluble organic matter. . , . 

Mineral matter 

Bitumen soluble 88° naphtha 

Soluble bitumen removed by 
H2SO, 

Total bitumen as saturated 
hydrocarbons 

Bitumen soluble in 62° naph- 
tha 

Bitumen insoluble in CCI4 . . 

Fixed carbon 



GILSONITE 


GRAHAMITE 


1.044 


1.049 


1.171 


Brown 


Brown 


Black 


Lustrous 


Lustrous 


Dull 


Sub-con- 


Sub-con- 


Hackly 


choidal 


choidal 




2 


2 


Brittle 


260°F. 


300 °F. 


Intumesces 


275°F. 


325°F. 


Intumesces 


0.9% 


2.3% 


0.1% 


1.2% 


4.0% 


0.5% 


99.0% 


99.9% 


94.1% 


0.0% 


0.0% 


0.2% 


0.0% 


0.1% 


5.7% 


47.2% 


15.9% 


0.4% 


87.7% 


71.8% 


25.0% 


5.9% 


4.5% 


0.32% 


67.4% 


30.3% 


0.7% 


0.0% 


0.4% 


68.7% 


13.0% 


13.4% 


53.3% 



Manjak resembles grahamite and is obtained from Barbadoes 
and South America. Its lack of uniformity and its high price have 
prevented any large use of it for American pavements, although 
it is used successfully in preparing other materials. 

Fluxing Solid Bitumens. — Paving materials are made from solid 
bitumens by fluxing them wdth petroleum residuums by two 
methods. In the first method the residuum is heated to above 
the temperature at which the solid bitumen melts and the latter 
is then added. Grahamite does not melt but intumesces and the 
residuum to flux it must be raised to an exceptionally high tem- 
perature. The mixture is agitated until the bitumen is all 
melted and the combined material is of uniform quality. 

In the second method, the residuum is heated to about 350°F. 
and air is then blown through it for six to forty hom's, depending 
upon the quality of the old and the properties desired in the fin- 
ished product. As soon as it reaches the proper consistency the 
blowing is stopped and enough solid bitumen mixed with it to 
give a paving material having the required properties. 



ASPHALTIC MATERIALS FOR ROADS^ 

The selection of bituminous materials for road purposes should 
be based upon the local climatic conditions, the volume and 
character of the traffic, the character of the stone to be used, 
and the type of road to be constructed or maintained. Such 
conditions manifestly call for expert advice. The requirements 
of several state highway departments are given here merely as 
indicating the way in which speciaHsts have met the needs of 
their respective localities. ^ 

Some of the requirements for road oils can be met by a few 
crude asphaltic petroleiuns. Prevost Hubbard gives the accom- 
panying analysis of a crude CaUfornia petroleum of this char- 
acter. This oil contained a small amount of water, and care in 
heating it would be necessary to prevent foaming. Hubbard 
says that "this oil is capable of increasing greatly in consistency 
after application and would serve as an excellent binding medimn." 

* Revised by Provost Hubbard, chief of road materials tests and re- 
search, United States OflBce of Public Roads. 

2 Among the engineers to whom this chapter was submitted was F. H. 
Joyner, Road Commissioner of Los Angeles County, California, who pre- 
pared the following comment, which illustrates forcibly the necessity of 
the services of a specialist in extensive road improvements: 

"From a study of the notes you submitted made by my assistants and 
myself, and from reports of the chemist and chief road oiler, we reached 
the decision that our study and conclusions on what we call road oils are 
of value only here in California, where we use only the native oils. While 
there is much in the notes that would not be applicable to our California 
oils or asphalts, I do not believe it would be necessary or proper to propose 
any changes in the notes." 

The following statement by W. Arthur Brown, chemist of the Los 
Angeles county road department, explains the views mentioned by Mr. 
Joyner : 

"The desirable constituent of a first-class road is asphalt. The asphalt 
carpet coat demands an oil that contains the highest grade of asphalt. It 
also demands that this asphalt be thin enough to spread well. It should 
enter all the interstices of the road surface. When the lighter constituents 
of the oil have served their purpose, namely, that of carrier and distribu- 
tor, they are no longer needed, in fact, they are not needed except, possi- 
bly, in very small amount. They should then be of such a nature that they 
will volatilize readily. We do not wish a possible volatile constituent that 
is solid or nearly so in cold weather but thin and acting as a fluxing agent 
in hot weather. 

The specification of the Los Angeles county highway department is a 
departure from, and simpler than, the older ones requiring fixed carbon, 
asphaltene, viscosity, float test, loss on heating during a certain number 
of hours at a specified temperature, ductility test, etc. This specification 
requires that the oil be reduced on the Brown evaporator in a specified 
time. This test determines the percentage of asphalt and insures the 

124 



A8PHALTIC MATERIALS FOR ROADS 125 

Crude California Petroleum Adapted for Road Work 
(From Provost Hubbard's Dust Preventives and Road Binders) 

Character Black, viscous, sticky. 

Specific gravity 25725°C 0.984 

Flash point, degrees C 160 . 

Loss at 100°C., 7 hours, per cent 5.25 

Character of residue More viscous than crude 

Loss at 163°C., 7 hours, per cent 16.4 

Character of residue Sticky, very viscous 

Loss at 205°C., 7 hours, per cent 30.0 

Character of residue Solid, not brittle 

Soluble in CS2, per cent 99.77 

Organic matter insoluble, per cent 0.12 

Inorganic matter, per cent 0.11 

Bitumen insoluble ill 86° naphtha, per cent 9.8 

Fixed carbon, per cent 2.05 

Viscosity, mentioned in this table, is explained by Prevost 
Hubbard as follows : 

If it is desired to apply a rpad binder at a given temperature, as for 
instance when it is to be heated by means of steam, a determination of its 
viscosity at that temperature is often of value. The test also serves as 
a means of identification. When a viscous material is to be cut with one 
of lower viscosity in order to bring it to a proper consistency for applica- 
tion, the actual viscosity of the mixture should be ascertained and not 
calculated from that of the two constituents for the reason that this prop- 
erty is not additive. 

In reporting the results of the test, the temperature of the 
material, the quantity used in testing, and the time in seconds 
taken by the material in flowing through a short tube of standard 
dimensions in what is called an Engler viscosimeter, are recorded. 
The longer the period of time taken by the material in flowing 
through the tube, the greater its viscosity. 

The float test is employed in determining the relative con- 
sistency of very viscous materials. The results are reported in 
seconds of time that a float containing the material under test 
will remain floating in water at a stated temperature. It is con- 
sidered a very useful test in controlling the preparation of road 

volatile oil being ot such a nature that it will leave the oil when once it is 
applied on the road. The percentage of asphalt is also much nearer the 
actual in the oil than by the methods of heating in an oven at a lower 
temperature. These specifications also require a stickiness test. This 
stickiness test, made on the Brown adhesivemeter, when interpreted in 
accordance with the entire specifications, especially with the time to reduce 
to asphalt, determine whether the oil has sufficient binding properties to 
hold the particles from displacement from each other and from the base. 
The stickiness and loss are standardized against road oils found on the 
market throughout California. The results of the tests have been carefully 
compared with actual service results, which are in accord with laboratory 
results in every case so far known." 



126 



AMERICAN HIGHWAY ASSOCIATION 



oils from given materials, for by continuing the heating until 
the residue gives a predetermined result in the float test, a imi- 
form product will be obtained. 

The ductility test shows the distance in centimeters that a 
briquette of the material will stretch before breaking, when 
pulled at the rate of 5 centimeters per minute. The briquette 
is 1 cm. square at the smallest section and has a cross-section 
of 2 square cm. at the cHps, which are 3 cm. apart. 



State Requirements for Asphaltic Materials for Penetration Roads 



Specific gravity, 25725°C 

Flash point, degrees C, min 

Ductility at 25°C., centimeters, 

min 

Penetration, 100 gr., 5 sec, 

25°C., mm., min 

Loss at 163°C., 5 hrs., per cent, 

max 

Character of residue 

Bitumen soluble in CS2, per 

cent, min 

Pure bitumen products 

Bermudez products 

Cuban products 

Trinidad products , 

Solubility in 86° naphtha, per 

cent 

Solubility in CCI4, per cent , 

Fixed carbon, per cent 



UXiINOIS 



Grade A Grade B 



1.000+ 
163 

50 

5-12* 

6 
Smooth 



99.5 
95.0 
80.0 
65.0 

72-85 



8-16 



0.97-1.00 
200 

15 

5-8 

2 
Smoothf 

99.5 



72-80 

99.4+ 

7-14 



Grade 
A-1 



0.97+ 
180 

30 

9-16t 

5 



99.5 
95.0 
81.0 
66.0 

72-85 

98.9+ 

8-16 



NEW 
YORK 



Grade 
A 



0.97+ 
190 

40 

14-19 

5 



99.5 
96.0 
81.0 
66.0 

70-88A 






45 

9-15 

6 



99.0 



98.5 



* 8-12 for material with 90 per cent total bitumen, 7-10 for material 
with 80 per cent to 90 per cent bitumen and 5-8 for Trinidad material 
having less than 80 per cent bitumen. 

t Penetration of residue at least 60 per cent of that of the original 
material. 

t 9-12 for pure bitumen products, 12-16 for fluxed native asphalts. 

§ Penetration of residue at least half that of original material. 

A In 76° naphtha. 

Note — Illinois specifies a brittleness test as follows: ''A cylindrical 
prism of the bituminous binder 1 cm. in diameter, after being maintained 
at a temperature of 5°C. (41°F.) for 20 minutes, shall bend 180 degrees 
at any point without checking or breaking." New York specifies a tough- 
ness test as follows: ''It (the bituminous material) shall show a toughness 
at 32°F. not less than 15 cm. Toughness is determined by breaking a 
cylinder of the material If inches in diameter by If inches in height in a 
Page impact machine. The first drop of the hammer is from a height of 
5 cm. and each succeeding blow is increased by 5 cm." New York also 
specifies a maximum of 4.7 per cent of paraffin. 



ASPHALTIC MATERIALS FOR ROADS 



127 



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128 



AMERICAN HIGHWAY ASSOCIATION 



State Requirements for Asphaltic Materials for Surfacing 





NEW 


YORK 




OHIO 






Grade 
H. 0. 


Grade 
C. 0. 


Grade 
H. 0. 


Grade 
M. 0. 


Grade C. 


Specific gravity, 25725°C 

Flash Point, degrees C 


0.96 

163 

* 

10 


0.93 

52 

t 
30 


0.96 


0.93 


0.91 


Ductility at 20°C., cm 








Loss at 163°C., 5 hours, per cent . 
Character of residue 


5 


25 


30 

Sticky 
99.5 

90-98 


Bitumen soluble in CS2, per cent. 
Solubility in 86° naphtha, per 
cent 


99.5 

75.90t 

6-14 

4.7 


99.5 

80-95t 
10 
4.0 


99.5 

80-94 
6 


99.5 

85-97 
3.5 


Fixed carbon, per cent 


3 


Paraffin scale, per cent 













* The residue after evaporation to 10 mm, penetration at a tempera- 
ture not exceeding 500°F., must amount to 85 to 95 per cent of the original 
volume and have a ductility of at least 25 cm. 

t In 76° naphtha. 

I The residue after evaporation to 10 mm. penetration at a temperature 
not exceeding 500°F. must amount to 50 to 65 per cent of the original 
volume and have a ductility of at least 25 cm. 

Note — New York specifies the following toughness test: Grade H. O. 
shall show a toughness at 32°F. not less than 20 cm, determined by the 
Page impact test. Ohio requires a viscosity of 10 to 60 at 100°C. for 50 cc. 
for Grade H. O., 40 to 80 at 50°C. for 50 cc. for Grade M. O., and 5 to 12 
at 50°C. for 50 cc. for Grade C. O. 

Shipping Road Oil. — Small quantities of road oil are shipped in 
tight wooden 50-gallon barrels, such as are used for shipping 
molasses, or in steel barrels. These barrels make the oil cost 2 
to 3 cents a gallon more than the price for the oil itself. Unin- 
jured empty barrels can generally be resold to the shipper. 
Heavy oil is troublesome to remove from barrels, and they are 
usually dumped into the open heating kettles and broken up. 
When the oil is warm the broken pieces of wood are raked out 
and used for fuel. If there is no heating kettle on the job, the 
barrels of heavy oil must be kept close to a fire or in a very warm 
room before the oil can be poured from them into the distributor. 

Larger quantities of oil are shipped in tank cars, holding 8000 
or 12,000 gallons. Where a large amount of oil is to be used 
annually near any railway, it will be desirable for the officials to 
supply a tank into which the oil can be run as soon as the car 
arrives. The season for roadwork is limited and during it there 
is a brisk demand for tank cars. The oil company which loses 
the service of a car for a week or ten days, while it stands on a 
siding waiting to be emptied, is obliged to add an equivalent 
item to its overhead expense, and the road district which provides 
for prompt discharge of tank cars is in a position to demand, 



ASPHALTIC MATERIALS FOR ROADS 



129 



and will probably get, quotations shaded somewhat to recognize 
its sense of business fairness. 

If oil must be used hot, a | or 1-inch steam connection must 
be made with the heating coils of the tank car. For this reason, 
the car is often spotted on a siding near an electric station or 
mill, but the steam can also be furnished by a road roller, trac- 
tion engine or other convenient source. It will take from twelve 
to twenty-four hours to heat a tankful of heavy oil to 150° to 
170°F., which is high enough to allow it to be pumped. The 
temperature can be increased after that in the distributor. The 
amount of steam supplied to the heating coils of the car is regu- 
lated by a valve on the exhaust pipe of the coil, which is adjusted 
to prevent a waste of steam. As some road oils have a low flash 
point, great care must be taken to prevent any oil coming in con- 
tact with a flame. The temperature of the oil should be tested 
from time to time with a thermometer, to see that it is not over- 
heated. If there is any water in the oil it will give a great deal 
of trouble if heated quickly, and if foaming is detected the rate 
of heating should be checked at once. 



Specific Gravities, Degrees Baume, Weights in Pounds per Gallon and Volume 

in Gallons per Pound of Oils at 60°F. Having Specific 

Gravities Exceeding 1.00 



SPECIFIC 


DEGREES 


POUNDS 


GALLONS 


SPECIFIC 


DEGREES 


POUNDS 


GALLONS 


GRAVITY 


BAUM^ 


PER GALLON 


PER POUND 


GRAVITY 


baum6 


PER GALLON 


PER POUND 


1.00 


0.00 


8.328 


0.1201 


1.15 


18.91 


9.577 


0.1021 


1.01 


1.44 


8.411 


0.1189 


1.16 


20.00 


9.660 


0.1009 


1.02 


2.84 


8.495 


0.1177 


1.17 


21.07 


9.744 


0.0997 


1.03 


4.22 


8.578 


0.1165 


1.18 


22.12 


9.827 


0.0985 


1.04 


5.58 


8.661 


0.1153 


1.19 


23.15 


9.910 


0.0973 


1.05 


6.91 


8.744 


0.1141 


1.20 


24.17 


9.994 


0.0961 


1.06 


8.21 


8.828 


0.1129 


1.21 


25.16 


10.077 


0.0949 


1.07 


9.49 


8.911 


0.1117 


1.22 


26.15 


10.160 


0.0937 


1.08 


10.74 


8.994 


0.1105 


1.23 


27.11 


10.243 


0.0925 


1.09 


11.97 


9.078 


0.1093 


1.24 


28.06 


10.327 


0.0913 


1.10 


13.18 


9.161 


0.1081 


1.25 


29.00 


10.410 


0.0908 


1.11 


14.37 


9.244 


0.1069 


1.26 


29.92 


10.494 


0.0889 


1.12 


15.54 


9.327 


0.1057 


1.27 


30.83 


10.577 


0.0877 


1.13 


16.68 


9.411 


0.1045 


1.28 


31.72 


10.660 


0.0865 


1.14 


17.81 


9.494 


0.1033 


1.29 


32.60 


10.743 


0.0853 



Note: For a similar table of oils of specific gravities less than 1.00 
see page 112. 

Pumping Road Oil. — In order to remove the oil from the tank 
car to the distributors, some form of pump is generally necessary, 
for it is not often that the car can be placed on a siding or trestle 
high enough to allow it to be emptied by gravity. 



130 AMERICAN HIGHWAY ASSOCIATION 

If a lift pump set in the top of the car is used, it should be a 
3 or 4-inch size. With it one man can fill a 600-gallon dis- 
tributor in twenty minutes. 

In many cases a hose or pipe is connected to the bottom of 
the car and run to an oil pump, operated by a steam or gasoline 
engine, which forces the oil into the distributor. A 1| or 2-inch 
power-driven rotary pump will dehver 600 gallons in ten to fif- 
teen minutes. These pumps work with either hot or cold oil. 
A water tank pump can be used with cold oil but hot oil will ruin 
the valves speedily. A 2-inch suction tank pump will fill a 600- 
gallon tank in thirty to forty minutes. 

The hose used in the connections between the pump and the 
bottom of the tank car should be as short as possible because the 
oil often destroys it rapidly. It is desirable to have a cut-off 
valve in the connection pipe. When everjrthing is coupled ready 
for use, the discharge valve in the bottom of the car is raised by 
means of a vertical stem running up to the dome of the car, and 
the flow of oil is controlled by the cut-off valve, for the manipu- 
lation of the tank valve is quite troublesome. 

Heating Road Oil. — As the fixed and operating charges at an 
oil storage plant are about the same irrespective of the amount 
of oil deUvered into distributors, it is desirable to load as many 
carts daily as practicable, in order to reduce the unit cost of such 
work. In California, where large amounts of oil are used in sur- 
facing concrete roads, oil stations have been designed with par- 
ticular attention to effecting such economics. It is considered 
desirable to have the oil at a temperature of 300° F. when it is 
applied, so it is heated to 325° for deUvery within 10 miles and 
350° for longer deliveries. 

The oil is discharged from the cars into storage tanks or pits 
holding 10,000 to 25,000 gallons. These contain steam coils to 
warm the oil sufficiently to enable it to be pumped into a circu- 
lating tank holding 2000 to 3000 gallons, where it is heated 
further by steam coils. The oil is then pumped through a heater 
and back into the circulating tank imtil its temperature is about 
200°, after which the temperature of the heater is raised and the 
oil pumped through it into the distributor. The whole operation 
takes one and one-half hours. 

The heater resembles a return tubular boiler. The furnace 
has a fire brick arch and walls and is heated by oil burners. The 
heated gases pass over the furnace arch in a chamber formed of 
ordinary brick masonry, and finally escape through a steel stack. 
The oil is pumped through a multiple grid of 3-inch pipes. The 
design is made on the assumption that with furnace temperatures 
of 1800° to 2000°, 1 square foot of heating surface will transmit 
3 British thermal units per hour per degree of change in temperature. 



ASPIIALTIC MATERIALS FOR ROADS 



13J 



Volume of Oil at 60°F. Equivalent to Unit Volume at Stated Temperatures in 

Fahrenheit Degrees 



O-F 





10 


20 


30 


40 


50 


60 


70 


80 


90 
















1.000 
0.962 
0.926 
0.893 
0.862 


0.996 
0.958 
0.922 
0.890 
0.859 


0.992 
0.954 
0.919 
0.886 
0.856 


0.988 


100 

200 
300 
400 


0.984 
0.947 
0.912 
0.881 


0.980 
0.943 
0.909 
0.877 


0.977 
0.940 
0.906 
0.875 


0.973 
0.936 
0.903 
0.871 


0.969 
0.933 
0.899 
0.868 


0.965 
0.929 
0.896 
0.865 


0.951 
0.916 

0.883 
0.853 



Note : This table is based on the assumption that the volume of oil 
increases 0.4 per cent for every increase of 10°F. above 60°. This rule 
is exactly applicable only to some oils. In Los Angeles County, Cal., the 
rate of increase in volume is taken at 0.3 per cent in the specifications of 
the county road department. 

Purchasing Oil. — Oil increases in volume from 0.3 to 0.4 per 
cent for each 10°F. rise in its temperature. The oil is bought 
on the basis of its volume at 60°F. and if measured at any other 
temperature its volume must be computed, or, in the case of an 
oil having an increase in volume of 0.4 per cent per 10°F., the 
accompanying table will give the volume at 60° with a minimum 
amoimt of figuring. To use it, multiply the tabular number 
for the temperature at which the measurement was made by 
the measured quantity of oil. For example 1,100 gallons of oil 
at 375°F. multipUed by 0.888 gives 978 gallons as the volume 
at 60°F. If the rate of increase per 10°F. was 0.3 per cent, the 
volume at 60°F. would be 995 gallons. 



TAR AND TAR PRODUCTS^ 

The tar used in roadbuilding is obtained by refining the crude 
tar produced in the destructive distillation of coal, in making en- 
riched water gas and in certain classes of coke ovens. It is a com- 
plex mixture of many hydrocarbons and is not a simple chem- 
ical substance. 

In a city gashouse, gas is produced by heating coal in retorts 
usually about 8 feet long, 15 inches high and 18 inches wide. 
The tar is driven off with the gas and is collected for the most 
part in ''hydraulic mains" which act as water seals for the gas. 
The gas is further cooled in a condenser, where more tar is de- 
posited, and the remaining tar is removed in a tar extractor 
and scrubbers. The tar obtained at each stage in the process 
is different from that obtained at the other stages, but all of it 
is usually run into large wells, where the accompanying ammo- 
niacal water rises and is drawn off. The character of the tar 
varies greatly. It is much affected by the temperature at which 
the coking is conducted, as well as by the character of the coal 
used. High temperatures result in an increase in the amount of 
free carbon in the tar, and this increase in free carbon is accom- 
panied by an increase in specific gravity. The presence of ammo- 
niacal water with oils distilling below 110°C. is stated by Pre- 
vost Hubbard to be the distinguishing features of all crude coal 
tars. 

Another class of tar is obtained from by-product coke ovens. 
The retorts in this case are much larger but are operated in much 
the same way as the retorts of illuminating gas plants, except 
that the main endeavor is to produce the maximum amount of 
coke instead of gas. For this reason the temperatures are lower 
than those usually employed in coal-gas works and the tar is 
likely to have a comparatively low amount of free carbon and a 
comparatively high amount of oils. There are several types of 
by-product coke ovens, and some produce tars better suited for 
road work than other types. 

Water gas is made by passing steam over hot coal, in which 
process no tar is produced. This gas is a mixture of hydrogen 
and carbon monoxide, and burns with a flame of no value for 

^ Revised by Prevost Hubbard, chief of road materials tests and research, 
U. S. Office of PubHc Roads. 

132 



TAR AND TAR PRODUCTS 133 

illumination. It must therefore be mixed with hydrocarbons, 
which are usually obtained by cracking a grade of petroleum dis- 
tillate called gas oil. In the purification of this enriched or "car- 
buretted" gas, tar is obtained which is called water-gas tar. 
It is lighter than coal tar and the water it contains is practically 
free from ammonia, which is an identifying characteristic of this 
material. It has a comparatively high amount of heavy oil and 
a low amount of pitch. 

In some gas works both coal gas and water gas are made and the 
tar from both processes are collected together, resulting in mixtures 
which may vary greatly in composition. 

The crude tar is stored in tanks at the refineries, each class 
by itself. As much water is removed by settling as is possible, 
since this is the cheapest method of getting rid of it. After set- 
tling, the tar is pumped into a still. Sometimes the tars from sev- 
eral sources are mixed so that a product with certain character- 
istics can be obtained which are unattainable by refining tar from 
one source. The stills are set in brick Uke horizontal boiler shells 
and are heated very carefully at first to prevent the water in the tar 
from causing foaming. The vapors from the still are liquified in 
condensers. Water and light oils are first driven off, then inter- 
mediate oils and finally heavy oils. The road materials are ob- 
tained from the residuum. The distillation must be stopped 
early if a fight road tar is desired, while the process is carried 
much further if a binder is desired. In the final stages, the con- 
tents of the still are agitated by jets of air to prevent coking. 

The composition of several crude tars and of the heavy pitches 
made by refining them is given in the accompanying table. The 
figures must not be considered more than representative of gen- 
eral characteristics, for individual tars in the same class vary 
greatly. 

Tar products for road purposes are called ''straight-run" when 
they are the residuums left after refining crude tars to the degree 
which will furnish a material of suitable composition, and "cut- 
back" when they are made by fluxing a hard pitch with a lighter 
distillate. 

The effect of free carbon in tar upon its utility for road purposes 
has been a subject of protracted controversy. Philip P. Sharpies 
makes this comment: 

Experience has seemed to settle that a moderate amount of free carbon 
is beneficial in a road tar, thus bearing out the practical experience gained 
in the use of coal tar materials in other directions. At the same time, an 
excess of free carbon is not desirable, since it tends to make the material 
difficult to work and also reduces to a considerable degree the amount of 
true bitumen available. On the other hand, a certain percentage of free 
carbon seems to enhance the binding power of the refined tar. The upper 



134 



AMERICAN HIGHWAY ASSOCIATION 



-< 
« 



e 

CO 

Eh 












c3 
Ph 



& 
Ph 

a 

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- 


1 


O 

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i-H 
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CO 

1-H 




00 

CO 




CO 

o 

d 






1.074 
0.3 
1.6 


1-H • 


O '; 

d 




VERTICAL GAS, 

PROVIDENCE, 

R. I. 




(M 

T-HO 

T— 1 


i—i 


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1.153 

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1.187 
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1.238 
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CO 

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HORIZONTAL 

GAS, 

ASTORIA, N. Y. 


o 


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1.267 
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HORIZONTAL 
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16th street, 

NEW YORK 


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TAR AND TAR PRODUCTS 135 

limit may perhaps be set at 25 per cent for a binder and perhaps 22 per cent 
for a tar used for hot surface application. The lower limits on these classes 
of materials should certainly not be less than 12 per cent for binder mate- 
rials and 10 per cent for hot surfacing materials. With cold surfacing 
materials the free carbon is necessarily much lower, as its presence in large 
quantities reduces the penetration. With cold surfacing materials 4 per 
cent may be placed as a desirable minimum. 

Prevost Hubbard makes the following comments on free car- 
bon in his Dust Preventives and Road Binders: 

In tars of the same consistency, those of low carbon contents have a 
greater inherent binding strength than those of high-carbon contents. 
In tars whose bitumen contents are of the same consistency those of high 
carbon contents have a greater inherent binding strength than those of low 
carbon contents, but the binding capacity of the former is lower. In sand- 
tar mixtures containing a relatively large amount of high carbon tar, the 
carbon may act as a filler and add to the mechanical strength of the min- 
eral aggregate, but better results in this respect can be obtained by the 
use of a smaller quantity of low carbon tar of the same melting point, 
together with a mineral filler. The waterproofing value of high-carbon 
tars is in general less than that of low-carbon tars. Free carbon retards 
the absorption of tars by porous surfaces. W^hen tar is exposed in 
comparatively thin films free carbon has little or no effect in retarding 
volatilization. 

Applying these facts to the use of tar in road treatment the following 
conclusions are logically deduced: (1) In the treatment of old road 
surfaces a low carbon tar is to be greatly preferred to a high carbon tar. 
(2) In ordinary bituminous road construction, both from the standpoint 
of efiiciency and economy, a low-carbon tar is to be preferred to a high- 
carbon tar whose bitumen content is of the same consistency. 

The distillation test of tars furnishes information regarding 
their utility for road work. Formerly the test was made on ma- 
terial which might or might not contain water, but the tend- 
ency of specialists at present is to remove any water from the 
samples by preliminary distillation at a low temperature, for no 
water is permitted in tar for hot appUcation under most speci- 
fications now. The distillation is carried on in an Engler flask 
and is conducted in a series of stages. The terminal tempera- 
tures of the stages have usually been 110°C., 170°C., 270°C. and 
300°C., but recently it has been proposed to make another stage 
with a terminal temperature of 235°C. The test is one which must 
be conducted with careful observance of the procedure speci- 
fied for the method followed or the results will not be comparable. 
The distillate obtained during each stage is called a ^'fraction." 

The 1916 requirements of several State highway departments 
for different grades of tar are given in the table on pages 136 
and 137. 



136 



AMERICAN HIGHWAY ASSOCIATION 











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BITUMINOUS ROADS' 

Bituminous materials are used on gravel and broken stone roads 
in three ways: (1) thoroughly mixed with the stone or gravel 
before the latter is placed on the roads; (2) driven into the 
interstices between the stone after the latter has been placed on 
the road; (3) applied to the surface of a finished gravel or broken 
stone road. The first method produces what is now commonly 
called bituminous concrete and the second method bituminous 
macadam. These will be described in this section and surface 
appUcations will be described in the next section. 

Rock for Bituminous Roads.^ — In bituminous road work obser- 
vations indicate that in some cases it is advantageous to use a 
rock of relatively high absorption rather than one with low 
absorptive quaHties, owing to a better adhesion of the bituminous 
material by a partial surface impregnation of the rock. 

While the binding or cementing value of a rock is a most 
important consideration from the standpoint of ordinary macadam 
construction, the same is not true of broken-stone roads which 
are carpeted or constructed with an adhesive bituminous material. 
The French coefficient of wear is also of relatively less importance, 
owing to the fact that the fine mineral particles produced by the 
abrasion of traffic combine, or should combine, with the bitumi- 
nous material to form a mastic which is held in place and pro- 
tects the underlying rock from abrasion so long as it is kept 
intact by proper maintenance. The toughness of the rock is of 
more importance, as the shock of impact is to a considerable 
extent transmitted through the seal coat and may cause the 
imderlying fragments to shatter. It would, therefore, seem that 
the minimum toughness of a rock for use in the construction of 
a bituminous broken-stone road or a broken-stone road with a 

^ It is the purpose of this chapter to indicate the methods followed in 
several sections of the country where bituminous roads have been built 
extensively rather than to recommend any methods as the best for all 
conditions. Revised by P. St. J. Wilson, chief engineer, United States 
Office of Public Roads and Rural Engineering; F. H. Joyner, road com- 
missioner of Los Angeles County, Cal.; and W. R. Farrington, division 
engineer, Massachusetts Highway Commission. 

2 From Bulletin 370, United States Department of Agriculture, "Physi- 
cal Tests of Road-Building Rock," by Prevost Hubbard, chemical engi- 
neer, and Frank H. Jackson, Jr., assistant testing engineer, Office of 
Public Roads. 

138 



BITUMINOUS ROADS 139 

bituminous-mat surface should, for light traffic, be no loss than 
for ordinary macadam subjected to the same class of traffic. 
For moderate and heavy traffic, however, the same minimum 
toughness should prove sufficient, owing to the cushioning effect 
of the bituminous matrix. No maximum limit of toughness need 
be considered for any traffic. 

In the case of bituminous concrete roads, where the broken 
stone and bituminous material are mixed prior to laying and 
consolidation, it generally appears advisable to set a minimum 
toughness of 6 to 7 for light-traffic roads, instead of 5, in order to 
insure that the fragments of rock which have been coated with 
bitumen shall not be fractured under the roller during consoUda- 
tion; and 12 or 13 for moderate and heavy traffic, instead of 10 
and 19, as in the case of water-bound macadam roads. 

Bearing in mind the fact that availability, cost, and various 
local conditions generally control the selection of proper limits, 
the accompanying table may be used as a general guide for 
minimum limits of the French coefficient of wear and toughness 
in connection with bituminous broken-stone roads. 

Bituminous Materials. — CHmatic conditions, the volume and 
character of traffic to be carried by a road, the kind of stone to 
be used, and the methods of construction vary greatly in differ- 
ent places and have an important influence on the determination 
of the bituminous materials to be used. For this reason it is not 
practicable to have a general specification of universal applica- 
bihty. The requirements for bituminous binders of a number 
of states are given in the tables on pages 126, 127 and 136. 

In most cases the binders are furnished by the contractors 
under specifications of greater or less detail. In Massachusetts 
the State highway commission usually purchases its material and 
furnishes it to the contractors, although contractors are occa- 
sionally required to supply it. 

Bituminous Macadam. — Roads of this type are frequently said 
to be built by the ^'penetration" method because the bituminous 
material is made to penetrate the interstices of the road from the 
surface. The grading, drainage and rolKng of the subgrade are 
carried out as in the case of waterbound macadam roads. On the 
subgrade is laid a base or bottom course, then a top course to 
which the bituminous material is applied, and finally a thin 
**seal'' coat of bituminous material covered with screenings or 
gravel to protect the main mass of the road from the weather 
and other deteriorating influences. 

The depth of the bottom course varies with the character of 
the subgrade, the traffic, the quality of the stone, the character 
of the top course and the preferences of the highway authorities. 
Probably 6 inches at the center and 4 inches at the sides are 



140 



AMERICAN 



HIGHWAY ASSOCIATION 



7- • u r rn. • 1 rr^sis of Rock for Bituminous Roads 
Limits of Physical T •' -' 

/T^ J J u T> >c 't Hubbard and Frank H. Jackson, Jr.) 
(Recommended by Frevos ' 



Broken stone with 
bituminous car- 
pet 

Bituminous macadam 
with seal coat 

Bituminous concrete . 



» MODERATE TRAVEL 



French 
coefficient 



At least 



Percent- 
age of wear 



Not over 



5.7 



Toughness 



At least 



MODERATE TO HEAVY TRAVEL 



French 
coefficient 



At least 



7 
10 



Percent- 
age of wear 



Not over 



5.7 



5.7 
4 



Toughness 



At least 



10 



10 
13 



^ „ r n-^ • TIT J ctl per Mile of Road for Different Rates of 

Gallons of Bituminous Materi^^''^l^^^^-^^ ' 



GALLONS 

PER 

SQUARE 

YARD 



0.20 

0.25 
0.33 
0.40 
0.50 
0.60 
0.67 
0.70 
0.75 
0.80 
0.90 
1.00 
1.25 
1.50 
1.75 
2.00 



"WIDTH OP KOAD IN FEET 



1,056 
1,320 
1,742 
2,112 
2,640 
3,168 
3,538 
3,696 
3,960 
4,224 
4,752 
5,280 
6,600 
7,920 
9,240 
10,560 



10 



1,174 
1,467 
1,936 
2,347 
2,934 
3,520 
3,931 
4,107 
4,400 
4,694 
5,280 
5,867 
7,334 
8,801 
10,267 
11,734 



■12 



,408 



T,760 
i,323 

;^,816 

i520 

5,224 

^-,716 

$928 

^280 

r,632 

S,336 

S,040 

^,800 

.^,560 

|X,320 

}2,080 



15 



1,760 

2,200 

2,904 

3,520 

4,400 

5,280 

5,896 

6,160 

6,600 

7,040 

7,920 

8,800 

11,000 

13,200 

15,400 

17,600 



18 



2,112 

2,640 

3,484 

4,224 

5,280 

6,336 

7,075 

7,392 

7,920 

8,448 

9,494 

10,560 

13,200 

15,840 

18,480 

21,120 



20 



2,347 

2,933 

3,872 

4,694 

5,867 

7,040 

7,862 

8,214 

8,801 

9,387 

10,561 

11,734 

14,668 

17,601 

20,535 

23,468 



22 



2,582 

3,227 

4,259 

5,163 

6,454 

7,744 

8,648 

9,035 

9,680 

10,326 

11,616 

12,907 

16,134 

19,361 

22,587 

25,814 



average depths.^ In MassE^?^^^^^*^' T^?^^ *^^ foundation is pre- 
pared very carefully, some 7^^ consisting of 12 inches or more 

of gravel or t elf or d, an irt^/ '""fo^^^^^'^fiKf,?: /""^ 
course 2 inches thick at the «^^^? and 3 inches thick at the center 
after rolling, except on st(f ^ foundations, where the standard 
thickness is 2 mches at al^ P^^^^^ ^^ ^^^ cross-section. These 
thicknesses are increased in.P^^.^ cases. n + ^u 

The Massachusetts specfS?^*'""^ «^" .^""^ ^™^"<l^ ^\'''\'' t^'*" 
those of most states, and S'^^ *^« ^^S^^^'''' ^^^ ^""^^ ^''^^""''^ 

. r\ J ^ 1.1. 2. en Dromiscs to bc heavy, it is often considered 

1 On roads where the traffic l entire width of the road, 
best to nave the same depth th( 



BITUMINOUS ROADS 141 

regarding the proportions of the ^ to 1^-inch size and the 1} to 
2|-inch size which shall be mixed together for this course, the 
intention being, where stone is crushed locally, to vary these 
proportions in order to use the output of the crusher. In New 
York and Pennsylvania the maximum size of the stone for this 
course is 3J inches. The Pennsylvania specifications require the 
stone to have a French coefficient of wear of not less than 10, 
and permit the use of gravel and of broken slag which weighs 70 
pounds or more per cubic foot, measured loose. In Ohio, if sand- 
stone is used in the bottom course, pieces as large as 6 inches are 
permitted; the maximum size with other rocks is 4 inches. In 
Illinois and California the maximum size is 3 inches. These 
variations are due mainly to differences in the average quality 
of stone available in the different states. 

After the stone has been spread, it is sometimes harrowed. The 
Illinois specifications call for the use of a tooth harrow weighing 
10 to 12 pounds per tooth. The course is then consolidated with 
a roller, one weighing 10 tons or more being generally required. 
It is next covered with screenings, small gravel and sometimes 
coarse sand, which are broomed and rolled dry until the inter- 
stices are filled, but not over-filled. Some engineers consider the 
course finished at this stage, while others require it to be sprinkled 
with water and rolled so as to consolidate it still further. 

On the work under a number of State highway departments, 
the stone for both the top and bottom courses must be shoveled 
from the carts into place, or be dumped on platforms and shoveled 
from there into place, or be spread over the road by distributing 
wagons built for the purpose. In other states the stone for the 
bottom course may be dumped on the subgrade and shoveled 
from these piles into its final place. Stone for the top course is 
never permitted to be dumped in piles on the bottom course. 
The screenings or other fine material used on the road are gen- 
erally required to be deUvered along the road before construction 
begins. 

Other types of bottom courses than those made of graded 
aggregates are occasionally used. Many macadam roads in good 
condition have had a bituminous macadam top course put on 
them. Macadam roads when in poor condition are often scari- 
fied, new material added where needed, and then rolled, thus 
furnishing a suitable bottom course at minimum expense. If 
these old roadways are thus used, their drainage should be care- 
fully examined and all defects remedied before the top course is 
laid. In the New York state highways, a base of run-of-bank 
gravel not larger than 3J inches is sometimes used. In this case 
the material passing a J-inch screen must not be more than 5 per 
cent in excess of the voids in the remainder of the material after 
this fine stuff has been removed. 



142 AMERICAN HIGHWAY ASSOCIATION 

In Massachusetts the top course is usually 2 inches thick, and 
as stone from IJ to 2^ is required the largest pieces become im- 
bedded slightly in the bottom course by the rolling. More than 
15 per cent of the f to IJ-inch stone, which is permitted in the 
bottom course, is not desired in the top course because experi- 
ence has convinced the Massachusetts engineers that its presence 
makes a less durable road. More bituminous binder is required 
with coarse than small stone, but the entire quantity can be 
applied at one time, while if small stone is used it has been 
found desirable to construct this course in two layers in order to 
be certain that the smaller voids existing with such stone are 
filled. 

The top course in most States is usually from 2 to 3 inches 
thick. 

The top course of the New York State highways is made of IJ 
to 2J inches stone, in Pennsylvania 1 to 3-inch, in Ohio 1| to 2J- 
inch stone for a course less than 3 inches thick and 2J to 4-inch 
stone for a course 3 inches or more thick, unless the stone has a 
loss on abrasion of less than 6 per cent, when the size is reduced 
to 2 to 3^ inches; in Illinois 1 to 2 J inches. The Ohio and 
Illinois specifications require it to be harrowed. 

In rolling this course, it is usually considered desirable to roll 
adjacent strips of the shoulders as well, so as to unite the shoulder 
and roadway as completely as practicable. It is also generally 
considered desirable to roll the stone until it is "locked" in place 
so the binder distributor can pass without leaving any impres- 
sion, but not to the maximum density. The reason for this is 
that the bituminous material is believed to be more uniformly 
distributed if the course of stone is capable of further compression 
after the binder has been applied. Some stone hard enough to 
carry travel should not be rolled heavily, for if heavily rolled the 
voids will be so reduced that the binder will not penetrate into 
them properly. 

No bituminous material should be applied except when the 
stone on the surface is clean and free from dust. The applica- 
tion is now made in many cases with a pressure distributor, 
which is required by some State highway departments ; it is also 
applied by gravity distributors and, on small work, by hand 
pouring cans. 

Distributing wagons often have some kind of fire-box for keep- 
ing the binder hot. Gravity distributors discharge their contents 
through nozzles or other spraying devices at their rear about 12 
inches above the road. The shape and location of the nozzles 
are so selected that the binder will be distributed uniformly 
over a strip of the road somewhat wider than the distance be- 
tween the wheels. The binder flows from the nozzles by gravity, 



BITUMINOUS ROADS 143 

and as the contents of the tank are drawn off the pressure on the 
nozzles decreases and the rate of flow per minute is reduced. 
In order to maintain a uniform flow, a control valve in the out- 
let pipe is provided. The rate of application of the material is 
regulated by this valve and the speed of the distributor. 

Pressure distributors are used where it is desired to have better 
control over the rate of application of the binder than is practic- 
able with gravity distributors, and also to obtain the best dis- 
tribution and penetration. In some types, compressed air or 
steam is admitted to the top of the tank so that the pressure on 
the surface of the binder, whether the tank is full or almost empty, 
is sufficient to drive the material through the nozzles with con- 
siderable force. In other types, the binder is driven out of the 
nozzles by a small pump. The nozzles of the pressure distrib- 
utors are generally about 6 inches from the surface of the road. 
In some cases the binder is forced through a hose ending in a 
nozzle which the operator moves along just above the surface of 
the road. 

Bituminous material is also distributed from tank wagons with- 
out any suitable piping and nozzles of their own. This is done 
by attaching to their rear end a light two-wheel sulky having the 
necessary distributing apparatus, which is connected by piping 
with the outlet of the tank wagon. Attachments are also made 
for this purpose which can be bolted to an ordinary tank wagon. 

Pouring cans resemble garden watering cans in appearance. 
The top is usually partly covered to prevent the binder from slop- 
ping out, and there is generally a removable screen which intercepts 
anything likely to clog the nozzle. The nozzle is a slot 6 to 10 
inches long, which is usually adjustable. A skillful man can 
apply bituminous material in this way very uniformly, but the 
expense on large work is gi'eater than with distributors. 

The binder can be heated in portable kettles, usually mounted 
on wheels, in distributing wagons, oil heating pits, or in tank cars, 
the method to be followed depending upon the amount of material 
to be heated. 

The amount of binder used is from IJ to If gallons per square 
yard, depending upon the depth and size of the stone. If an 
asphalt binder is used it must be applied at a temperature of 
about 300°F. and if tar at about 200° to 225°F. After it is spread 
it is covered with small stone, usually from about I to f inches 
in size; in New York State work stone of f to 1} inches is speci- 
fied. In Massachusetts good results have been obtained in 
some cases with sand. After this dressing has been spread it is 
often gone over with brooms to make certain that all voids in the 
surface are filled, and the material unformly distributed, and the 
brooming should be finished with the brooms working parallel with 
the line of the road. 



144 AMERICAN HIGHWAY ASSOCIATION 

After the top course has become firm under the roller, the 
surface is swept clean and the seal coat is applied. This is usually 
spread at the rate of J to J gallon per square yard, and is covered 
with i to |-inch stone chips or pea gravel. The road is then 
broomed, using a lock street broom for the purpose, and then 
given a thorough rolling as to consoUdate it as much as possible 
and the broom can be attached to the roller during this final rolling. 
A liberal use of both the hand broom and the lock street broom, 
or the broom fastened to the roller, during the screening and 
finishing of the road will do much to insure that the dressing 
is evenly taken up by the oil and a smooth riding surface obtained 
that will not start the pounding of automobiles and the con- 
sequent rippling of the surface. 

In the State highway work of Illinois, there are there courses 
and a seal coat in bitmninous macadam construction. The sec- 
ond course is 1 to 2i-inches stone, harrowed, rolled, and treated 
with 1 gallon of binder per square yard. This is covered with | 
to |-inch screenings, which are broomed into the voids and the 
excess swept off. A second application of binder is then made 
at the rate of | gallon per square yard and covered with torpedo 
gravel ranging in size from f-inch down to fine sand. This is 
broomed until the voids are filled, when the surplus is removed. 
Another application of binder is made at the rate of J gallon 
per square yard and covered with torpedo gravel at the rate of 
about 1 cubic yard per 200 square yards of road. The wheels 
of the roller may be wet to prevent them from picking up the 
binder; some engineers object to such wetting and require the 
wheels to be oiled. 

Where the grade is steep, the Massachusetts highway com- 
mission has recently tried the practice of leaving the surface 
rather rough, so as to afford a foothold for horses and resistance 
to skidding for automobiles. 

Bituminous Concrete. — When the stone and binder are mixed 
together thoroughly before they are placed on the road, it is prac- 
ticable to use both small and large stone and thus reduce the vol- 
ume of the voids to be filled with bituminous binder. This mate- 
rial is placed on any of the bottom courses used with bituminous 
macadam and also on concrete. It is essential for the bottom 
course to be dry and clean when the mixture is spread over it. 

The size of the stone required by different State highway 
departments varies somewhat, and some departments have a 
number of standard proportions. In Massachusetts crusher- 
run trap from J to 1| inches is specified for some roads, and also 
crushed gravel, which will be mentioned later. In New York, 
f to IJ-inch stone is used for a course 2 inches or less in thick- 
ness, and for thicker courses stone up to 2 J inches in size is 



BITUMINOUS ROADS 145 

allowed. In both New York and Maryland materials are per- 
mitted which will give a finished pavement with less than 10 
per cent passing a 2-mesh screen, 8 to 22 per cent passing a 4- 
mesh, 25 to 55 per cent passing a 10-mesh, 18 to 30 per cent 
passing a 40-mesh, 5 to 11 per cent passing a 200-mcsh, and 7 
to 11 per cent of bitumen. In Maryland a mixture is also used 
containing two parts of J to IJ-inch stone and one part of sand 
with 25 per cent passing a 20-mesh screen and 5 per cent passing 
80-mesh. To this mixture is added 5 per cent of powdered Hme- 
stone or cement and 7 to 9 per cent of bitumen. In Illinois the 
proportions are left to the engineer, but the purpose is to obtain 
the equivalent of a thorough mixture of 1 cubic yard of grit sand 
passing a f-inch ring with 40 to 80 per cent passing a 10-mesh 
sieve, and 3 cubic yards of J to 1^ inch stone with 30 to 80 per 
cent retained on a 1-inch ring. Instead of the stone 3 cubic 
yards of f to 1-inch gravel with 20 to 70 per cent retained on a 
|-inch screen may be used. 

The amount of bituminous binder on the Massachusetts work 
ifi about 20 to 24 gallons per cubic yard of stone. In New York, 
for the work with broken stone without fine material, 18 gallons 
are used per cubic yard of stone and the purpose is to have the 
finished course contain from 5 to 7J per cent by weight of bitumen. 
On the Illinois work, from 27 to 30 gallons of binder containing 
95 per cent or more of bitumen is used per cubic yard of stone or 
gravel, and if the binder contains less than 95 per cent of bitumen 
the quantity must be increased proportionately. 

Although stone and tar binder have occasionally been mixed 
cold, as in Rhode Island, it is customary to mix the stone and 
bituminous material hot. There is a marked difference of opin- 
ion regarding the temperature to which the stone should be heated, 
Massachusetts requiring this to be 180°F. or more and lUinois 
300° to 375°. A high temperature will injure some binders and 
not others, and it is therefore important to have the aggregate 
uniformly heated to the proper temperature for the binder used, 
the weather conditions, and the length of haul from the mixing 
plant to the road. The binder is heated in kettles or tanks. The 
temperature for asphalt is 275° to 375° and for tar 200° to 275°, 
the limits varying somewhat with the grades used. Special care 
must be taken to prevent overheating. Sometimes hot stone and 
cold binder are mixed. The mixing on small work can be done 
by hand, but is more quickly and thoroughly performed on large 
work in mixers made for the purpose. 

The best equipment for any contract will depend upon local 
conditions, among which the transportation of the mixed mate- 
rial is an important factor. The mixture must be delivered 
on the site at temperatures of 150° to 280°, according to the 



146 AMERICAN HIGHWAY ASSOCIATION 

binder used. The maximum permissible drop between the tem- 
peratures of the material at the mixer and when it reaches the 
road, freedom^ from segregation in the mixture, and the practi- 
cable speed of delivery, fix the maximum length of haul. If the 
maximum length of haul permits the use of a central plant for 
the whole work, it is often practicable to locate it at the crusher 
plant and save some labor charges. Portable plants for use along 
the road have been greatly improved in recent years and are used 
extensively. 

The wagons for transporting the mixture should be tight, and 
under some weather and hauling conditions their contents should 
be covered with canvas to keep them from becoming chilled. The 
bodies of motor trucks are sometimes jacketed or insulated for 
the same purpose. 

The mixture should be shoveled from the wagons, or dumped 
on wood or metal platforms from which it can be shoveled. The 
shovels are often heated, as are the rakes used in spreading the 
mixture. It is considered desirable by some engineers to pro- 
hibit delivering hot mixture on the road within one hour of 
sunset. 

When the edges of the pavement are not protected by a stone 
or concrete curb, the New Jersey highway department requires 
the contractor to place temporary curbs of 6 or 8-inch planks of 
the same thickness as the finished top course. 

"\ATLen it is necessary to lay half of the width of a road so as to 
allow traffic on the other half, the base of the first half is allowed 
to project about 2 feet beyond the center line of the roadway. 
The top course in such cases ends only a few inches beyond the 
center line, for this will insure all of it resting on a firm base. 
After the second half of the base has been constructed, the inside 
edge of the top course already laid is cut back vertically or nearly 
so along a straight or properly curved line so as to obtain a 
perfect joint with the second half of this course. 

After the material has been spread, it should be rolled imme- 
diately. Sometimes an initial compression is given with a 3- to 
6-ton tandem roller and the final compression with a 10-ton 
macadam roller, but the usual practice is to use a 7- to 10-ton 
roller giving 200 to 300 pounds per linear inch of roll. The 
wheels may be oiled to prevent the binder from sticking to them. 
This rolling is continued until the roller leaves no marks in pass- 
ing. Any places which can not be reached by the roller are 
rammed with a hot iron tamp. 

The road is often given a seal coat at the rate of ^ to J gallon 
of binder per square yard, which is at once covered with pea 
stone or grit. The binder is often the same material used in the 
bituminous concrete but sometimes it is a more fluid grade. 



BITUMINOUS ROADS 147 

Some engineers require it to be applied with a squeegee distributor. 
The seal coat is rolled until it is thoroughly incorporated with the 
top course. 

Mixed Gravel' Asphalt Roads. — The Massachusetts highway com- 
mission has built a number of roads with mixed gravel-asphalt 
surfaces on gravel and broken stone bases. The surfacing with a 
gravel base is 2J inches thick after rolling. The following notes 
from its 1915 report describe the construction: 

A road, 18 feet in width with 3-foot shoulders, was built everywhere, 
the curves being banked and widened to 21 feet. A gravel foundation was 
put in wherever the bottom was bad, and about 4 inches of local crushed 
stone was spread and well rolled. 

On this was spread, as evenly as possible, about 3 inches of a bitumi- 
nous mixture made of gravel that had been run through the crusher and 
sand or stone dust, mixed with a heavy asphaltic product. The gravel 
and sand and the asphalt were thoroughly heated and were mixed in a hot 
mixer, and then carted onto the road and spread. The surface was rolled 
down to about 2 inches in thickness when the mixture was sufficiently cool 
not to crawl under the roller. 

Great care is necessary to insure a uniform product, uniformly heated, 
mixed and spread, and that sufficient asphalt is used and no more than 
sufficient to bind the mixture properly. The quantity of asphalt has to 
vary somewhat, according to the amount of voids in the mineral aggre- 
gate. The variation is usually from 18 to 22 gallons of the hot asphalt to 
the cubic yard of gravel. When the mixture is right it has about the 
consistency of brown sugar and compacts under the roller, though when it 
is first spread and rolled it sometimes has a few hair cracks which the 
traffic soon irons out. The asphaltic product used in this work has a pene- 
tration of from 80 to 120 with a Dow penetrometer. 

Sand and Oil Roads. — In 1905 the Massachusetts highway 
commission surfaced a road at Eastham by distributing hot 
asphaltic oil over the sand which is practically the only material 
in the vicinity, applying 1| gallons to the square yard in two 
applications. The results were so encouraging that more sand- 
oil roads have been built and the experience thus gained has 
shown what are the requirements for success. They are now 
built by both the penetration or layer method and by the mixing 
method. They are considered suitable when the traffic is mostly 
light teams and automobiles and will not stand up if used daily 
by many heavily loaded teams. The average daily traffic in 1915 
on one succrssful layer road was 20 heavy teams, 17 light teams 
and 253 automobiles. On a mixed road it was 6 heavy teams, 
23 light teams and 505 automobiles; on another mixed road 21 
heavy teams, 38 light teams and 197 automobiles. 

It is desirable for success to use a hard, strong, sharp and well- 
graded sand, such as is abundant on Cape Cod, where this type 
of construction has been developed. Many sands are too fine, 
too uniform in size, too rounded or not strong enough. Fair 
results have been obtained with some fine sands, however. 



148 AMERICAN HIGHWAY ASSOCIATION 

An oil asphalt of good quality that will bind and not lubricate 
must be used. For the layer type, the preference in Massa- 
chusetts is for an oil with a viscosity of 150 to 200 seconds at 
200°C., using a Lawrence viscosimeter or about 1038 to 1384 
with 100 cc. at 100°C. in an Engler viscosimeter. From IJ to 
2 gallons per square yard are used, in two applications, with a 
covering of sand after application. In the mixed type, oil as- 
phalts having a penetration of 60 to 135 by the Dow penetrometer 
have been tried, but that now used ordinarily has a penetration 
of 90 to 125. From 16 to 22 gallons per cubic yard of sand have 
been used; the present average is 18 gallons. The Massachusetts 
commission advises testing each carload of oil before using it. 

In the layer type of construction, the commission spreads clay 
or loam over the sand subgrade to reduce the rutting of the sur- 
face by wheels and pitting by horses' hoofs when the oil cart passes 
over it. The oil is then spread evenly while hot with a dis- 
tributing cart and immediately covered with sand. This process 
is then repeated. 

In the mixed type of construction the sand and oil are mixed 
hot to form a mastic which is spread over the sandy subgrade 
and rolled. The subgrade is carefully shaped and hardened as 
in the case of the penetration type. The mastic sheet is about 
4 inches thick at the center and 3 inches at the edges. The best 
results have been obtained by keeping the road constantly shaped 
with a road scraper during rolHng, and a seal coat of | gallon of 
a lighter oil such as is used in layer work improves the surface 
and decreases maintenance charges. In the early work the sand 
was heated on sheets of iron, but this overheated parts of it and 
underheated other parts, so that now the heating is done in rotary 
heaters. 

If the traffic in the future proves too heavy for these roads, the 
commission believes they can be greatly improved and strength- 
ened at a moderate cost by using harder asphalt, greater care in 
grading the sand, and the addition of cement and stone dust. 
In this way a sheet asphalt pavement 2 inches thick can be laid 
on the old sand-asphalt road as a base. 

Asphalt Blocks on Country Roads 

As designed and manufactured for use on country roads, the 
asphalt blocks are 5 inches wide, 12 inches long, and 2 inches deep, 
weigh about eleven pounds each, and have a specific gravity of 
about 2.40. 

The asphalt block was developed and perfected on the theory 
that crushed trap rock, on account of its preeminent hardness and 
inherent grittiness, made the best known material for a roadway 



BITUMINOUS ROADS 149 

surface, the one thing needed being a cement, or binding material, 
to keep all of the particles permanently in place. This was accom- 
plished by the use of an asphaltic cement to bind together the prop- 
erly graded particles of crushed trap, the hot mixture being con- 
solidated by tremendous pressure into blocks so dense and free from 
voids as to be practicall}^ non-absorbent. In the asphalt block, 
therefore, we have an asphaltic concrete, or macadam, mixed, in 
exact proportions, at a central plant, under conditions insur- 
ing absolute uniformity, and receiving the compression necessary 
to produce a dense and non-absorbent material. 

Not only has a special block been produced, but a special method 
of construction has been worked out, designed to utilize what is 
left of the worn and rutted macadam road as a foundation for the 
blocks. This is accomplished by scarifying the surface, if necessary, 
filling up the deep ruts, rolling with a heavy steam roller, and lay- 
ing upon the surface of the old macadam, a bed of cement mortar 
about 1 inch in thickness, to serve the double purpose of forming 
a firm unyielding bed for the blocks, and binding them securely 
to the macadam foundation underneath. By this method the 
material used in the original construction of the road is not thrown 
away, but used as foundation for a permanent wearing surface. 
Where the old macadam is too thin, or too badly worn to be safely 
used as a foundation, it will be necessary to lay a concrete base, 
but usually there is broken stone enough in the old macadam to 
supply what is needed for laying concrete. 

A pavement may be laid of any desired width, contour, grade, 
or crown. It is perfectly feasible to pave one-half of the roadway, 
or only a narrow strip in the center, and extend the paved area 
at a later date as traffic necessities require, or as appropriations 
become available. It is not necessary to set curbstones or head- 
ing stones to border or define the 
paved area, since a row of stretcher 
blocks held firmly in place by a shoulder 
of mortar, as shown in the sketch, 
answers the purpose perfectly and 
leaves the entire roadway surface 
smooth and uniform. 

A good example of this construc- 
tion is on the Albany Post Road, through the villages of Hast- 
ings-on-Hudson, Dobbs Ferry, Irvington, North Tarrj^town, Town 
of Mount Pleasant, Briarcliff and Ossining, N. Y., on the Boston 
Post Road in Pelham Manor and Rye, N. Y., on 9 miles of road- 
way from Daytona to Deland, Volusia County, Florida, and on 
Nassau Street, Princetown, N. J., a section of the Lincoln Highway. 




BITUMINOUS SURFACE APPLICATIONS^ 

Surface applications vary widely in character, according to 
their purpose. In most cases such an application is essentially a 
maintenance measure, but in the case of the bituminous mats or 
wearing courses used in California, or the mats now laid on new 
water-bound macadam, the first cost of such work is essentially 
a part of the first cost of the improvement. The practice in 
making such surface applications of any general type varies 
widely in different parts of the country, more widely than the 
practice in any other branch of road work. Whether greater 
uniformity will prove desirable or the work can be done success- 
fully by a wide variety of methods can not be definitely deter- 
mined until the records of such work and of the traffic on roada 
are kept with more detail and uniformity than at present. The 
widespread interest in the subject was one of the leading charac- 
teristics of highway affairs in 1916, and was an evidence of the 
conditions mentioned. 

Oiling Earth Roads 

Surface applications on earth roads were made in California 
many years ago, and a method of incorporating oil and earth by 
a special form of roller was employed for some time. More 
recently well built earth roads in Iowa and Illinois have received 
surface applications as a maintenance measure. The experience 
in these states shows that while some success follows applications 
on roads that are not in good condition, it is very desirable to 
have the surface properly shaped and hard before the oil is applied. 
The oil binds the grains of earth together and reduces the dust, 
but it does not give the resistance to attrition which a hard sur- 
face affords. The treatment is therefore one which must be 
regarded as adapted only for roads with light traffic and light 
vehicles. If sand instead of earth is present, the methods of con- 
struction first used in Massachusetts and described on page 147 
should be considered. 

If the road has ruts and holes in the surface and is poorly 
drained, water will collect in puddles, soften the oiled crust at 

^ Revised by George H. Biles, second deputy State highway commissioner 
of Pennsylvania, and B. H, Piepmeier, maintenance engineer of the Illinois 
State highway department. 

150 



BITUMINOUS SURFACE APPLICATIONS 151 

these places, and seep into the roadbed. The material under the 
crust will give way under heavy loads and the money spent in 
oiling will be largely lost, because the oiled material will become 
mixed with the unoiled material below and dust will be produced 
about as freely as on an unoiled road. Furthermore, the oiling 
of a mudhole often aggravates troubles due to such a defect. 

The surface to receive the application must be dry, or the oil 
will not penetrate the pores, and it must be free from dust, for 
the oil forms flakes or scales with the dust and these are a worse 
nuisance than plain dust, being very irritating to the eyes. 

Both cold and hot applications have been used successfully in 
Iowa, but the State Highway Commission prefers to heat the oil 
as it apparently gives enough better penetration to justify the 
additional expense. It is desirable to secure the advice of a 
specialist in selecting the oil. A light oil must be used and as 
it may have a low flash point, care should be taken to keep it at 
a temperature below its flash point and to prevent any of it 
coming into contact with a flame. The first application is made 
at a rate of about | gallon per square yard, and later applications 
at the rate of J to | gallon. The brief experience in such work 
indicates that two light applications annually for two years and 
afterward a single appKcation annually will be sufficient on a 
road adapted for such treatment and not subject to traffic requir- 
ing a more durable surface. During 1916 the Illinois State high- 
way department issued the following advice on the work. 

The best results may be secured during the first application, by apply- 
ing either a cold oil or at least a very thin product that will penetrate the 
surface of the road several inches and at the same time contain as many 
binding elements as possible so as to seal all pores in the earth, making it 
waterproof and at the same time adding some binding qualities that may 
assist the bond of the soil itself. A suitable product, as is commonly 
expressed, may vary from 30 to 60 per cent in asphalt. After the surface 
of the road has been thoroughly saturated, a hot oil or a slightly heavier 
product may be used. 

If the heavier oils are used for the first application they will not readily 
penetrate the surface of the road and will consequently form a mat on 
top. The forming of the mat before the surface of the road is more or less 
waterproof may be a serious fault as moisture will accumulate beneath the 
mat and the road will be much slower in drying out than it would had the 
oil not been applied. The mat surface with a soft subsoil will rut more 
readily, besides breaking and scaling off in large pieces, making the road 
surface rough and undesirable. 

The Illinois authorities recommend covering the oiled surface 
with clean, hard sand, at the rate of a cubic yard to 100 to 150 
square yards. 



152 AMERICAN HIGHWAY ASSOCIATION 

Broken Stone Road Surfacing 

It has been found that a surface application on a new water- 
bound macadam road may prove unsatisfactory, although if the 
road is exposed to traffic for three months the desired results are 
obtained if the treatment is properly carried out. This is prob- 
ably due to the large amount of fine, lightly-bound dust on the 
roadway, which is removed by the early traffic, or to the greater 
stability of the road as a result of its consolidation by traffic. 
In New York, macadam roads finished so late in the fall that they 
can not have three months wear before winter, are given a surface 
application of calcium chloride as a temporary protection against 
raveling during the months that must elapse before bituminous 
surfacing can be placed. 

In making thin surface applications to an old road that is thick 
enough to carry the prospective traffic and has a surface in fair 
condition, the ruts and holes must first be patched. This is best 
done several days in advance of the surfacing. Each hole or 
rut is swept clean,^ painted with bituminous material and filled 
with f to 1| inch stone and binder. The stone and binder are 
often mixed at a central point and carted along the road by the 
patching gang, for use where required. Just before the surfacing 
is done, the road is swept thoroughly, often with some type of 
revolving broom. Sometimes wire brooms are used first and then 
fiber brooms. The oil is applied hot or cold according to quality 
at the rate of about f to | gallon per square yard, as the engi- 
neer considers best, and then covered with clean screenings, granu- 
lated slag or gravel at the rate of about 60 pounds per square 
yard. It is advisable to secure the advice of a specialist in 
selecting the oil. The oil is applied by hand on small work, but 
usually with a distributor. If the screenings are distributed by 
hand they should be previously deposited in piles at convenient 
intervals along the roadside. They are also distributed by 
spreader carts. The length of time the road should be closed to 
traffic depends upon the weather, character of the oil, and the 
amount of screenings used, varying from 1 to 48 hours. 

If the road oil rises through the screenings, or ''bleeds," in hot 
weather, more screenings should be spread over those places. If 
the road is used mainly by automobiles, a thin covering of screen- 
ings is sometimes spread first and later a covering of sand or other 
fine material, to act as a filler and prevent the tires from dislodging 
the screenings. 

The following rules for the amount of bituminous material to 
be used in surfacing broken stone roads were prepared by George 
H. Biles, second deputy highway commissioner of Pennsylvania: 

1 It is desirable to cut the edges of a hole so as to secure vertical faces 
to which the new material will adhere properly; a patch with a feather edge 
is liable to be unsatisfactory. 



BITUMINOUS SURFACE APPLICATIONS 153 

If the surface of the road is made up of pieces of ballast size stone 
(3-inch) from which traffic has removed all the fine material, leaving large 
surface voids between the stone, enough of the bituminous material must 
be applied so that it will flush up level to the top of the large pieces of stone 
and firmly bind the chips and gravel which lie in the crevices between the 
stone. 

If, on the other hand, the surface of the road is equally clean, but traffic 
has not removed the fine particles between those stones to the same extent, 
and the crevices between them arc consequently smaller, then a somewhat 
smaller amount of bituminous material should be used, since an excess 
will again flow off the road. 

In treating a road which has recently been resurfaced, it will be found 
often that even after all the screenings and fine material have been swept 
from the top of the road leaving the large stones bare, there will still be a 
certain amount of dust and fine material between the stones which has 
not yet been compacted thoroughly by traflSc and which will absorb the 
bituminous material like a blotter, leaving only a brown stain in these 
spaces. In such cases, the amount of application must be increased until 
this fine material is well saturated and there is enouprh of the bituminous 
material near the surface of the road to bind thoroughly the covering of 
chips or gravel. 

The first application of a bituminous surfacing to a waterbound 
macadam road may be disappointing. The hoofs of horses are 
liable to dislodge the mat and the surface will have a spotted 
appearance. After several applications, however, the macadam 
surface will become protected everywhere. 

On the New York State highways which are thick enough to 
carry the traffic but are too rough to be treated satisfactorily with 
cold oil and screenings, surfacing with two applications of hot 
oil is sometimes done. After the old road is patched and cleaned, 
it is covered with 0.4 to 0.6 gallon of oil to the square yard, over 
which just enough 1-inch stone is spread to cover the surface. 
This is rolled lightly and then covered with 0.3 to 0.4 gallon of 
oil per yard. This is covered with J inch stone in the thinnest 
possible layer, which is rolled as soon as the oil is cool enough to 
permit it. 

On the Illinois highways, when a double application is made, 
about J gallon per square yard is used on each application, and 
the preferred covering is torpedo sand, | to f inch in size, but 
clean, stone chips are also employed. The total amount of cover- 
ing material with such a treatment is one cubic yard for each 125 
square yards of road. When a single application is made ^ to 
^ gallon of oil per square yard and a cubic yard of torpedo sand 
for every 150 square yards of road are employed. 

Bituminous sandstone obtained in Kentucky has been used in 
parts of that state for re-surfacing old macadam. The latter is 
scarified, smoothed with a road machine, and enough new stone 
added to give the desired thickness and contour. This is rolled 
thoroughly and then covered with pulverized bituminous sand- 



154 AMERICAN HIGHWAY ASSOCIATION 

stone to a depth of about IJ inches, loose, when spread. It is 
desirable to allow the sun to shine on the loose material for a few 
hours, until it appears slightly oily, and then roll it, slowly at 
first and later more rapidly. 

Concrete Road Surfacing 

While surface applications to concrete roads have been em- 
ployed in a number of states, there is no agreement as to their 
desirability. They have been used to the greatest extent in 
California, where both thin wearing surfaces and an asphaltic 
mixture are used. The following information concerning both 
types was supplied by Austin D. Fletcher, State highway engineer 
of California. 

The thin bituminous wearing surface is about half an inch in thickness 
when completed. After it has been under traffic for a few months it is 
found to contain a fairly uniform mixture of mineral aggregate and bitumi- 
nous binder consisting of about 8 to 11 per cent of bitumen and the balance 
mineral aggregate of a fairly uniform grading running from dust to rock 
of 5 -inch maximum diameter. It shows no tendency to flow or creep and 
the surface remains true and free from rolling. The concrete base, how- 
ever, must be finished with a true, smooth surface to make a good riding 
highway as this type of surfacing is not thick enough to smooth up to any 
considerable extent a concrete pavement whose surface is uneven. 

The procedure in laying this thin wearing surface is as follows: First 
the surface of concrete is cleaned of dirt, dust films and any thin coat of 
laitance. This is best accomplished by opening the bare concrete to 
traffic for a month or two. The iron shod traffic and the rapidly moving 
rubber tires are of greatest help in breaking any weak layers of dirt or 
laitance and exposing the surface of the concrete proper. This "traffic 
cleaning" is followed by brushing with revolving street brooms and hand 
brooms. In some cases flushing the surface with water is a help in wash- 
ing off any thin coat of clay. It is of greatest importance that the asphaltic 
oil bind to the solid concrete and not to any overlying weak film of dirt. 
The care taken in getting a clean concrete is without doubt in a large 
measure responsible for the success of this surfacing because of the strength 
of the bond between the concrete and the bituminous wearing coat. The 
few failures where the wearing surface has been stripped from the con- 
crete have been nearly always easy to trace to a pavement improperly 
cleaned prior to the application of the road oil. 

After the concrete has been cleaned the asphaltic oil is applied by a 
pressure distributor at the rate of |- gallon per square yard. This oil 
surface is immediately covered by a layer of either crushed rock screenings 
or fine gravel of | to ^ inch. This material may contain some fines and 
dust but should be fairly clean. 

The screenings are applied by shoveling from piles placed at frequent 
intervals alongside the road. The shovelers can be taught to so throw 
the screenings that they will cover the road surface with a fairly uniform 
thickness. The road can now with advantage be given a light rolling but 
this is not necessary. Any excess screenings should be swept into piles 
alongside of the road to be used on the second application of road oil. This 
is applied on the second application at the same rate and is covered with 
screenings as before. 



BITUMINOUS SURFACE APPLICATION 155 

The road is now thrown open to traffic and during the first two weeks 
may require further screenings to take up excess oil. The traffic is of great 
assistance in forcing the screenings into the oil and compacting and mak- 
ing a homogeneous carpet on the concrete. 

The oil is applied to the road at a temperature of from 250° to 300°. 
It contains approximately 90 per cent of 80° penetration asphalt. In 
California the road oil companies classify this product as a "90-80" road 
oil. 

In building the thin bituminous wearing surface for concrete pavements 
two physical properties of the road oil are of greatest importance. First 
the oil must be of such a viscosity that when applied to the road it will 
readily combine with the screenings that are thrown upon its surface. 
A very viscous oil will form a hard surface and the screenings will lie 
there without being absorbed and to a large extent be thrown off the road 
by the passing traffic. Only a small amount will settle or be forced into 
tne oil and the surface will not build up into a satisfactory protecting 
wearing coat. 

The second physical property of great importance is that the road oil 
must be cementing or adhesive so that it will bind tightly to the concrete 
surface and bind together all of the fragments of stone screenings. It 
should be an active cement and if it is not sticky then the wearing sur- 
face will not be firm enough to resist the push and pull of the passing 
traffic. 

The State highway routes leading from the great centers of population 
have required a higher type of surfacing to meet successfully the demands 
of heavy traffic. 

After proper curing of the concrete its surface is cleaned of all dirt and 
dust films and given a paint binder coat composed of asphaltic cement 
and engine distillate of lightest gravity. The asphalt used has a penetra- 
tion between 80° and 90°, the mix being one part asphalt and one to two 
parts distillate, the exact proportion of distillate being determined by 
trial. The satisfactory mixture is one that paints the concrete with a thin, 
uniform, glossy black film which becomes hard two hours after application. 

The surfacing used has the following composition expressed in per- 
centages: 

Bitumen soluble in carbon disulphide, Vg-lO 

Aggregate: 



PASSING 


REFUSINQ 


200 sieve 




80 " 


200 sieve 


40 " 


80 " 


10 " 


40 " 


4 " 


10 " 


2 " 


4 " 


2 " 





8-13 
14-25 
17-29 

5-11 

1 f^OK 


per cent 


ID— ZO 

3-10 





100 " 

The asphaltic cement used has a penetration of from 70 to 90 degrees, 
District of Columbia standard, and passes the usual requirements for 
solubility, volatility and ductility. The heating of asphalt, aggregates 
and dust and mixing and laying follow the usual practice. 

Prior to the laying of the surfacing, the testing laboratory makes grad- 
ing tests of such sand, limestone dust and rock screenings as will be avail- 
able for the work and selects such of these that give the desired mix. In 
this selection the following points are considered important: 

Let a be taken as the percentage of asphaltic cement that will be used 
in the finished material. Then the dust passing the 200-mesh sieve should 
at least equal a-l. The fine sand passing the 80 mesh and retained on 



156 BITUMINOUS SURFACE APPLICATIONS 

the 200 should be approximately 2a. If the available sand is high on the 
finer sieves a may be taken as high as 9.5 per cent. If the sand is coarse, 
a may be as low as 8 per cent for the trial mix. The coarse aggregate pass- 
ing the No. 2 sieve and retained on No. 10 should be from 28 to 35 per cent 
of the other mix. If these points are satisfied by the available material 
the weights of coarse aggregate, fine aggregate, dust and asphaltic cement 
can be given to the road crew for a trial batch. Under field working con- 
ditions a trial batch will show if the mix is "wet" or "dry" and by a slight 
change in the percentage of asphaltic cement a mixture can be made that 
will rake and roll properly. In this way the mineral aggregate is not 
changed but kept under known satisfactory grading. As the work pro- 
ceeds, grading tests should be run at frequent intervals on the different 
mineral aggregates to insure a uniform grading in the finished pavement. 
Analysis of samples of the different batches should also be made to check 
the uniformity of the mix. 

The surface after thorough rolling should have a specific gravity in 
excess of 2.20 if the sands and crushed rock screenings are of average spe- 
cific gravities. A sample of the finished pavement taken each day and 
tested for specific gravity will indicate if there has been insuflBcient com- 
pression, either due to method of rolling or to the surface being too cold 
when rolled. 



BRICK ROADS^ 

Brick pavements have been used on the streets of American 
cities for many years and the United States Bureau of the Census 
reports that in 1909 they formed nearly 24 per cent of the entire mile- 
age of paved streets in 158 cities. Some of the early brick pave- 
ments gave satisfactory service for many years, but others did 
not. The unsatisfactory early experience was due in part to 
the use of unsuitable materials, in part to the improper recon- 
struction of pavements cut to permit laying pipes, and in part 
to the defective methods of construction employed, just as was 
the experience with other types of block pavements. It is not 
possible to build lasting block pavements unless the blocks are 
prevented from setthng, which results in holes in the surface, 
or from tilting over on their bottom side, called "turtling,'* 
which results in a rounding of the upper edges of the blocks, 
called ''cobbUng." These defects led to better methods of 
construction, so that when bricks came into use on country 
highways success was assured if municipal experience was taken 
as a guide. There are always communities as well as persons 
unwilling to profit by the experience of others, however, and con- 
sequently some brick roads have been built of poor materials 
and by poor methods with the inevitable unsatisfactory results. 
Such unfortunate experience was unnecessary then and is un- 
necessary today; it was largely due to ignorance of the requu'e- 
ments for good work, carelessness, lack of proper supervision, 
and a desire to cheapen the cost of such roads below the amount 
needed for proper construction. 

Paving Bricks 

Paving bricks are made from a great variety of shales and fire 
clays and consequently bricks of equal worth vary considerably 
in appearance. Shale contains iron which makes shale bricks 
red when burned under normal oxidizing conditions and brown 

^Revised by William W. Marr, chief state highway engineer of Illinois; 
A. H. Hinkle, deputy highway commissioner of Ohio; P. M. Tebbs, engi- 
neer of construction of the Pennsylvania State Highway Department; 
Will P. Blair, secretary of the National Association of Paving Brick Manu- 
facturers; and W. C. Perkins, chief engineer, R. T. Stull, ceramic engi- 
neer, and F. A. Churchill, of the Dunn Wire-Cut Lug Brick Company. 

157 



158 AMERICAN HIGHWAY ASSOCIATION 

or nearly black when burned under reducing conditions. Fire 
clays have less iron than shales, the iron being present in a com- 
bined state, and bricks made from them are buff-colored, unless 
reducing conditions during burning darken them. The shales 
and fire clays are often unsuited for making paving bricks as they 
occur, and then material from one stratum in a pit must be 
mixed with that from another stratum or that from one pit with 
that from another, and sometimes with sand or surface clay. 

The raw materials are crushed and ground dry in large revolv- 
ing pans under heavy rolls, called "mullers." This material is 
screened to remove pieces of too large size, and is then conveyed 
to a pug mill, in which the materials are mixed somewhat as 
concrete is mixed in a continuous concrete mixer. Here enough 
water is added to convert the material into a thick mud, which 
is beaten by the revolving blades into a condition of uniform 
consistency and composition. This mud is fed continuously 
into a brick machine, where it is forced by an auger through a 
die, whence it emerges as a fairly hard bar of rectangular section, 
which is cut mechanically into bricks. This bar of hard clay may 
be approximately 4 by 4| inches in section, in which case it is 
cut about every 9 inches, forming ''end-cut" bricks, or it may be 
approximately 9 by 4^ inches in section and cut every 4 inches, 
forming ''side-cut" bricks. These bricks are sometimes sub- 
mitted to a reshaping process before drying, in which case they 
are called "re-pressed" bricks, and sometimes they are dried as 
they are finished by the brick machine, in which case they are 
called "wire-cut" bricks. For drying, the bricks are placed on 
cars which are run very slowly through a long, tunnel-like heater, 
into which hot dry air is admitted continuously. After remain- 
ing on the cars in the tunnel about twenty-four hours their 
weight is reduced from 15 to 20 per cent. The bricks are then 
ready for burning, one of the most important steps in the manu- 
facturing process. The bricks are stacked in kilns in such a 
way that the heated air circulates freely around them, and great 
care must be taken in the regulation of the temperature through- 
out the entire burning process, from the time the kiln is first 
warmed until it is cool enough to permit the withdrawal of the 
bricks. 

In laying paving bricks a space is left between successive rows 
for the material which forms the joints, and as it is very desir- 
able for these joints to be of a uniform width, one side of a paving 
brick has either two or four lugs, which are small projections 
from the surface of the bricks.^ These projections serve to keep 

* There are some bricks which do not have lugs but have raised letters 
or four projections, one near each corner, on one face. Raised letters are 
not permitted on bricks for Ohio State roads. 



BRICK ROADS 159 

the adjacent faces the proper distance apart when the bricks are 
forced into contact during the paving operations. These pro- 
jections extend | to J inch from the side or face. In one class of 
side-cut bricks the cutting is done by wires which are moved 
across the bar of clay so as to produce the lugs needed on one side 
of the brick. These are called "wire-cut lug'' bricks. In an- 
other type of side-cut bricks, 2|, 3 and 4 inches deep, the ribs 
are moulded on one of the sides as it comes through the die. A 
wire-cut side is placed on top in laying such bricks, wliich are 
called ''vertical fiber" bricks in some parts of the country. Other 
types of projections are made by devices attached to the brick 
machine. In the case of repressed bricks, the projections from 
one or both sides are made in the press. 

There is no universal standard size for bricks but the tendency 
seems to be toward 3.^ inches width, 4 inches depth and 8^ inches 
length, with a permissible variation of | inch either way in the 
width and depth and J inch either way in length. The depth is 
occasionally reduced as much as an inch for roads having light 
traffic, when the monolithic and cement-sand cushion types of 
construction, explained later, are used. 

"Hillside" bricks are made for use on grades of 5 per cent or 
more. They have one or more grooves cut the full length of the 
bricks, along their edges, in the case of bricks to be laid in the 
usual manner, or two grooves cut transversely in the case of bricks 
to be laid parallel with the curb. These grooves are about f inch 
deep and are intended to prevent shpping of horses or automo- 
biles. Bricks with beveled edges are used for grades, notably on 
the carriage ramps of the Pennsylvania Terminal in New York, 
where the travel is very heavy, and quite generally on grades ex- 
ceeding 5 per cent, throughout Ohio. 

Tests of Bricks 

The color of the interior of bricks from the same plant gives 
an indication of their quality, for generally the color is darker 
in the bricks burned with the higher temperatures. The color of 
the exterior of the bricks is a less rehable indication of quality, 
and even interior color is of little or no value in judging the bricks 
from different plants. The other features of bricks which can 
be determined by visual inspection are explained in the follow- 
ing description of the bricks which may be rejected under the 
standard specifications of the American Society for Testing 
Materials: 



160 AMERICAN HIGHWAY ASSOCIATION 

All bricks which are broken in two or chipped in such a manner that 
neither wearing surface remains substantially intact, or that the lower or 
bearing surface is reduced in area by more than one-fifth.^ 

All bricks which are cracked in such a degree as to produce defects such 
as are defined in (the previous paragraph) either from shocks received in 
shipment and handling, or from defective conditions of manufacture, 
especially in drying, burning or cooling, unless such cracks are plainly 
superficial and not such as to perceptibly weaken the resistance of the briok 
to its condition of use. 

All bricks which are so off-size, or so misshapen, bent, twisted or kiln- 
marked, that they will not forma proper surface as defined by the paving 
specifications, or align with other bricks without making joints other than 
those permitted in the paving speoifioations. 

All bricks which are obviously soft^ and too poorly vitrified to endure 
street wear. 

Formerly a number of different laboratory tests of the properties 
of paving bricks were required by specifications, but today reli- 
ance is placed mainly on the rattler test to determine their qual- 
ity. Its name is derived from the use of a foundry rattler, em- 
ployed in cleaning iron castings, in making the first tests of this 
kind on bricks. The rattler used today is constructed specially 
for the purpose. It is an iron and steel barrel of the cross-section 
of a 14-sided polygon, about 20 inches long and 28 inches in diam- 
eter, inside dimensions, with a shaft projecting from each end. 
This barrel is mounted in a frame with the shafts horizontal and 
can be revolved by power. 

Ten dry bricks are weighed and placed within the rattler, 
together with an abrasive charge consisting of 10 cast-iron spheres 
weighing from 7 to 7| pounds each and a sufficient number of 
cast-iron spheres from If to If inches in diameter and weighing 
from 0.75 to 0.95 pound each, to make a total charge of 300 
pounds. The rattler is then revolved 1800 times at the rate of 
29-2 revolutions per minute. In this way the bricks are sub- 
jected to innumerable blows which are considered to imitate the 
conditions of service more nearly than any other test yet de- 

1 Mr. Tebbs makes this comment: ''The area of a standard brick is about 
30 square inches and I consider about one-fifth or 6 square inches a very 
large allowance. I think that a reduction of not more than one-tenth of 
the area should be permitted." This comment is not approved by Mr. 
Blair on the grounds that experience has shown no ill effects from the rule 
of the Society, and to limit the reduction of area to 10 per cent, would in- 
crease materially the cost of the bricks. 

' Mr. Tebbs advises adding the words, "not uniformly vitrified, badly 
laminated." The phrasing of the standard specifications was debated at 
great length before adoption, and uniform vitrification was not adopted 
as a requirement because no brick is uniformly vitrified, strictly speak- 
ing. The words "badly laminated" are sometimes used, but objection 
has been raised to them as not conveying to the inspector the meaning of 
the engineer, which is to reject bricks having laminations that are separate 
one from the other, sometimes called 'open" laminations. 



BRICK ROADS 



161 



vised. When the test is finished, the bricks are taken out, all 
pieces of them weighing less than 1 pound are discarded, and the 
remainder are weighed. The loss in weight during the test, 
expressed as a percentage of the original weight, is the form in 
which the results are stated. 

The percentage of permissible loss in the rattler test is fixed 
at different amounts in order to meet the conditions imposed by 
differences in travel and the experience of different localities with 
bricks of various grades. The American Society for Testing 
Materials gives the following scales of maximum permissible 
losses for different classes of travel : 





CHARACTER OF TRAVEL 


MAXIMUM PERMISSIBLE LOSS 




Average 


Single brick 


He aw 


22 
24 
26 


24 


Medium 


26 


Light 


28 







The New York and Pennsylvania State highway departments' 
specifications call for the medium-travel grade and Ohio and 
Illinois for the heavy-travel grade. In Illinois the wire-cut 
lug bricks are given 1 per cent higher permissible loss than the 
repressed bricks, which must conform to the tabulated require- 
ments. In that State there is a minimum permissible loss spec- 
ified, 17 per cent for wire-cut and 16 per cent for repressed bricks. 
The average permissible maximimi loss may reach 25 per cent 
for wire-cut lug bricks if no individual brick loses more than 
28 or less than 20 per cent, and may reach 27 per cent if the 
range of loss of every individual brick is between 29 and 23 per 
cent. With repressed bricks, the average loss may reach 24 
per cent, with a range of 27 to 19 per cent for every individual 
brick, and 26 per cent with a range of 28 to 22 per cent. These 
requirements put a premium on uniformity in the bricks, which 
many engineers regard as of importance in preventing unequal 
wear of the siu-face of a brick road. They hold that where soft 
and hard bricks are laid together indiscriminately, some of the 
bricks are worn away more rapidly than where a pavement is 
laid with bricks of a more uniform quality. 

In New York and Ohio 30 bricks form a lot for sampling. 
These represent the hard, medium and light-burned bricks de- 
livered on the job, and each grade is tested separately. During 
testing there is a large percentage of failures in the abrasion test, 
partially caused by the selection of fight and hard-burned brick. 
The laboratory results obtained on such bricks serve as a guide 
in throwing out or culling part of the bricks on the job. 



162 AMERICAN HIGHWAY ASSOCIATION 

Some years ago the crushing strength and specific gravity of 
paving bricks were considered properties which should be speci- 
fied, but experience has shown that it is unnecessarj^ to do so. 
The specific gravity of fire-clay bricks averages between 2.1 and 
2.25 and that of shale bricks between 2.2 and 2.4. The crushing 
strength of good paving bricks ranges from 10,000 to 20,000 
pounds per square inch, when the test load is applied over the 
entire top surface of the specimens, and may be higher if only a 
part of the surface is loaded. This is from five to ten times the 
probable maximum load on a pavement. 

The capacity of a brick to absorb water was formerly consid- 
ered an important indication of its porosity, and low porosity 
was held to be essential for strength and good sanitary proper- 
ties, which were then considered as particular advantages of 
brick pavements. With the improvements that have been made 
in the rattler test and the increased knowledge of the slight in- 
fluence of a wide range in porosity upon the sanitary value of 
such pavements, the absorption test has lost much of its former 
favor among roadbuilders. It affords useful information in 
comparing bricks made under identical conditions and for other 
research work, and it is still required by a few State highway 
departments. In Ohio, the bricks taken from a rattler after 
testing in that apparatus must not absorb more than 3J per cent 
of their weight of water during immersion for forty-eight hours. 
In Pennsylvania, the absorption of thoroughly dried bricks im- 
mersed in water for twenty-four hours must not exceed 3| per 
cent. 

Another test, formerly used extensively, probably because the 
apparatus for making it was available in many schools and easily 
obtained, is the transverse or cross-breaking test. It is now 
little used outside of New York and New Jersey. In the former 
State the test required by the highway department is to place 
the sample brick on edge on two parallel supports 6 inches apart 
and load it at the center until it breaks. If the distance in 
inches between the supports is represented by L, the load in 
pounds which produces rupture by W, and the width and depth 
in inches of the brick by b and d respectively, the modulus of 
rupture will be SWL/2bd?, which must not be less than 2000 
pounds in bricks for New York state work. 

Curbs 

Curbs are required along the sides and ends of brick pave- 
ments laid on a sand cushion or laid on natural soil and having 
sand-filled joints, in order to hold the bricks at those places and 
also, with some types of base, to hold the material of the base in 



BRICK ROADS 163 

place. Planks have been used, but their short life compared with 
that of the pavement makes them undesirable, for nobody can 
foretell whether they will be renewed as they wear out. In 
some places stone slabs can be obtained for the purpose at prices 
which enable them to be used economically. Vitrified curbs are 
sometimes used, but require more careful bedding than stone 
curbs, because their shorter length and lighter weight render 
them more subject to displacement. Concrete is most gener- 
ally used for curbs. In country highway work the top of the 
curb is usually flush with the surface of the pavement. If a con- 
crete base is used, the curb is usually an integral part of it, and 
is generally from 6 to 8 inches wide on top. If a concrete base 
is not used, the depth of the curb must be governed mainly by 
the character of the subgrade, the frost hazard and the character 
of the shoulders. In any case it is desirable to have the top 2 
inches of the concrete curb not leaner than a 1:2:3 mixture, 
finished with a wooden float, and the outer surface should be 
spaded. This spading is done by placing a spade in the form 
against the outer plank and rocking it back and forth so as to 
force the coarse aggregate of the fresh concrete away from the 
face. 

Where the bricks are bedded on mortar or green concrete, 
most engineers believe that curbs are not needed. ^ If they are 
omitted special care must be given to providing firm shoulders 
along the marginal bricks. 

The Base 

A brick pavement requires an absolutely firm un5rielding sup- 
port. An old macadam road thoroughly underdrained and se- 
cure against settlement or upheaval ,is considered a satisfactory 
support by some engineers. But it is rarely possible to find such 
a road, for usually the drainage is defective, the cross-section has 
too much crown, or the grades are wrong. It is then necessary 
to disturb the hard crust of the road and this is very likely to 
reduce materially its value as a foundation. In some parts of 
Florida, where frost is not to be feared, if the sand which pre- 
vails is held in place by curbs or planks and thoroughly rolled 
while damp, it makes a hard, unyielding support not subject to 
disturbance if good drainage is assured. On the other hand, the 
black soil of the prairie States, which absorbs water freely and 

1 Mr. Marr states: "Experience in Illinois demonstrates beyond ques- 
tion that curbs are not needed under such conditions. We have had sev- 
eral instances where the edges of the bricks were exposed at intersections 
to a grinding action of wheels striking them at acute angles, and there 
seems to be absolutely no danger of the bricks being loosened at the edges 
under any conditions obtaining in ordinary service." 



164 AMERICAN HIGHWAT ASSOCIATION 

parts with it slowly, is an unstable material and a strong con- 
crete foundation must be provided for brick roads built over it, 
so that any differences in the supporting capacity of the subgrade, 
from one season to another or between adjoining places in the 
road, are equalized by the concrete slab and do not cause waves 
in the brick surface. 

The methods of constructing the road bed and preparing the 
subgrade are explained in the chapter on earth roads. It is 
necessary to have a uniformly firm subgrade, and if there are 
heavy cuts and fills the grading must be done carefully. It is 
desirable to allow the subgrade to go through one winter before 
putting down the pavement, although this is rarely practicable 
under the usual working conditions. The drainage is particularly 
important, on account of the difficulty of improving it, if defec- 
tive, after the pavement is laid. 

If the subgrade is firm and well drained, a 6 to 8-inch base of 
good gravel, broken stone, vitrified clay^ or slag, thoroughly 
consohdated by rolUng, may prove sufficient for moderate traffic. 
Such a base should be built in two courses with all the care given 
to the best macadam construction. In some cases, second qual- 
ity paving bricks have been used for a base. The subgrade is 
covered with enough sand to give a depth of 2 inches after roll- 
iag with a hand roller. The No. 2 bricks are laid flat on thia 
cushion, parallel with the curb, and the joints are filled with fine 
sand. 

The best base for general use is concrete. A few years ago 
there was a general opinion that it should be 6 inches thick, but 
4-inch bases on well-built subgrades are giving satisfaction where 
frost action is not serious, and a thickness of only 3 inches or less 
is under consideration by some engineers. If a secure subgrade 
is provided, the best thickness is in part determined by the cost 
of the concrete. A 1 : 3 J : 6 mixture with ordinary materials, 
laid to form a 5-inch base, may be less expensive than a 1 : 2| : 5 
mixture of better materials laid to form a 4-uich base. If gravel 
is used as the aggregate, it is generally economical to screen it and 
then recombine it, if good concrete is desired. If good concrete 
is not desired, it will be better to leave out the cement entirely 
and use the money thus saved in putting down a good base of the 

^ Mr. Hinkle advises eliminating gravel and vitrified clay as materials 
for a base for this reason: ''While fair foundations may be made from 
these materials, it so frequently happens that poor foundations result 
from the use of these materials that I think it well to omit referring to 
them here and hence not encourage their use any more than necessary." 
Mr. Blair believes that the long experience with gravel foundations in 
places like South Bend, Ind., warrants their use. 



BRICK ROADS 165 

macadam type.^ The thinner the base, the better the concrete 
should be. A 4-inch base of poorly graded, dirty aggregate and 
a pinch of cement is an invitation to early failure. One common 
defect is insufficient mixing. This should be done in a batch 
mixer which should be run between 15 and 20 revolutions per 
minute, and after all the materials are in the mixer, the process 
should be continued imtil the mixer has made at least 15 revo- 
lutions. The surface of the concrete should be struck off by 
means of a transverse templet, drawn along the side forms, and 
be kept well wet for at least three^ days. No traffic should be 
permitted on the base for at least seven days after it is laid. On 
the Illinois state highways, if there are deviations exceeding i 
inch from the desired shape of the surface, they must be repaired 
if a sand-cement cushion, described later, is to be employed. 

The Cushion or Bedding of the Bricks 

One of the causes which contributed to hmit the serviceability 
of some early brick pavements was the imperfect way in which 
the bricks were supported on the base. The latter was covered 
with loose sand of inferior quality for its piupose, smoothed off 
roughly without being consolidated, and the bricks laid on it and 
driven to a bearing with a paver's tamper. The joints were 
then filled with sand and the roadway thrown open to travel. 
The surface was not smooth at the outset, traffic on it soon forced 
some bricks down more than others, and water percolating in 
cold weather through the joints into the sand cushion alternately 
froze and thawed, throwing the bricks into irregular positions. 
Under such conditions the edges of the bricks became chipped, 
and finally many of the bricks became broken and dislodged, 
leaving holes in the roadway. The lesson of this experience was 
so clear that for a number of years the importance of bedding 
the brick securely has been generally recognized. Today there 
are three methods of doing this, termed the sand cushion, sand- 
cement or dry mortar bed and monolithic or green concrete bed 
types. The purpose of each is to support the bricks securely at 
the proper elevation to give the pavement a smooth surface. 

Sand-Cushion Type. — A sand cushion is primarily intended to 
smooth out the inequalities in the top of the base, which were 
formerly greater than good practice now permits, to provide for 
the sUght variations in the depth of the bricks. Experience 

1 Mr. Tebbs advises the use of concrete exclusively as a base for brick 
pavements. Mr. Blair holds that experience at Cleveland, Terre Haute 
and other places shows that under proper conditions a base of other ma- 
terial will prove satisfactory. 

" Mr. Hinkle advocates at least five days. 



166 AMERICAN HIGHWAY ASSOCIATION 

shows that the sand must be free from large stones, which pre- 
vent satisfactory consolidation of the cushion, and some engi- 
neers hold that it must also be free from loam, clay and materials 
of a greasy nature when wet.^ Granulated slag is sometimes 
used instead of natural sand and is believed by some engineers to 
be superior to ordinary sand. Dry sand must be used, accord- 
ing to some engineers, on the ground that wet sand shrinks in 
drying and cannot be relied upon to support the bricks at the 
desired elevation. Other engineers believe that somewhat damp 
sand is more easily handled and gives as good results. The 
thickness of this bed in the case of city streets has usually been 
2 inches of late, but where a concrete base is used for a country 
highway and is finished so that no part deviates more than J 
inch from the true surface, a thickness of IJ inches is enough. 
On narrow roads where the concrete base is easily finished to the 
exact cross-section of the road, 1 inch is probably enough.^ 

The dry sand is cast over the base to a sKghtly greater depth 
than the proposed thickness of the cushion. The extra depth is 
usually about f inch where a 2-inch cushion is desired. A plank 
templet, which is often provided with a steel edge, is then drawn 
over it to smooth it down to the prescribed cross-section. If the 
roadway is less than about 25 feet wide, this templet is supported 
at the ends by the curbs. If the roadway is wider than 25 feet, 
the templet is long enough to reach from one curb to a longitu- 
dinal plank support at the center of the road. The sand is con- 
solidated and brought down to grade by rolhng it by hand, using 
a roller weighing 300 to 400 pounds. After rolling the surface 
is tested with the templet, the high spots reduced and the low 
places filled, and the rolling repeated. This process is repeated 
until a uniform surface at the desired elevation is obtained. The 
extra elevation of the templet in the first stage of the work is 

^ Mr. Tebbs makes the following comments: "Pennsylvania specifica- 
tions allow 15 per cent of loam and I advocate the use of a sand contain- 
ing loam, because it helps to bind it, thereby avoiding the shifting about 
which often occurs with clean dry sand. It has been proved that dry sand 
occupies less space than wet sand. Dry sand cannot always be obtained 
without considerable expense, and 1 therefore think it advisable to use 
reasonably dry sand without requiring that it be dried, and as thin a 
cushion as it is practicable to use. The cushion should be 1 inch or less. 
This decrease in the depth of the cushion minimizes the shrinkage due to 
the drying of sand which was moist when placed." 

^ Mr. Marr states: *'lt has been well demonstrated that the thinner 
the sand cushion between the rigid base and the brick wearing surface, 
the better, and its only function is to assure a smooth surface on the pave- 
ment. The use of the plain sand cushion is growing less every year and 
seems to have its greatest advantage in street paving where numerous 
subsequent openings may be expected and it is necessary to use a soft 
filler." 



BRICK ROADS 167 

obtained by laying strips of wood of the requisite thickness on 
top of the curbs or other supports of the templet. 

If a road carries only light vehicles, a well consolidated sand 
cushion is a satisfactory support for the bricks. Heavy vehicles, 
whether drawn by horses or self-propelled, are believed to jar the 
road although definite tests with a seismograph or a similar in- 
strument are needed to determine the correctness of this opinion. 
It is certain, however, that if the roadway contains a railway 
track the whole structure will be jarred by the cars traveling along 
it. The sand cushion is not considered by many engineers to 
be a satisfactory support for bricks hkely to be jarred, on account 
of the possibility that the repeated minute vibrations in it may 
cause parts of it to shift their position. This apprehension has 
led to the use of the sand-cement bed. 

Sand-cement Cushion Type. — The cushion consists of a dry 
mixture of one part of cement with three to five parts of mortar 
sand. These materials must be thoroughly mixed dry. If the 
cushion is to be 1 inch thick, as in Pennsylvania state work, the 
mixture contains less cement than if it is to be J inch thick as 
in the Illinois State work. The loose material is given about \ 
inch greater depth than the desired thickness of the finished bed. 
The mortar is spread and shaped like a sand cushion. In Illi- 
nois, where the sand-cement bed has been used extensively, the 
shaping of the bed for the brick is considered of prime importance 
and the State highway department requires the contractor to 
employ skilled men for this part of the work. 

There is a difference of opinion as to the best method of moist- 
ening the sand-cement bed to convert it into mortar. Some 
engineers hold that the bricks should be laid on the dry bed and 
rolled, and then the pavement should be sprinkled sufficiently 
to allow water to pass down the joints into the bed. This 
wetting down should be done as soon as the bricks have been 
rolled. The Pennsylvania highway department requires the 
mortar bed to be sprinkled lightly just before the bricks are laid. 
In any case, the mortar bed should not be laid so far in advance 
that any of it will remain exposed over night, and if any of it be- 
comes wet and the cement sets it must be replaced by dry material. 

Monolithic Type J — The monolithic or green concrete bed is not 
actually a cushion, for the bricks are laid on the fresh concrete 
base as soon as it has been finished. In this type of work steel 
side forms for the base are generally specified and curbs are 

^ A monolithic brick pavement was laid about 1904 in Terre Haute, Ind., 
on the recommendation of Street Commissioner Varrelman of St. Louis. 
It was on a railroad teaming yard and a private street to the warehouse of 
Hullmann & Company. This is probably one of the earliest uses of the 
type in this country. 



168 AMERICAN HIGHWAY ASSOCIATION 

omitted. The steel forms are considered necessary as supports for 
the heavy steel templet which is used. 

The concrete is placed in successive batches for the entire 
width of the pavement in a continuous operation. This concrete 
as placed has a slightly greater depth than the finished thickness 
of the base, and the workmen are guided in placing it by a light 
wood templet which rests on the side forms when in use. When 
it has been brought to a smooth surface of the desired shape, it 
is finished with a steel templet. This consists of a 6-inch steel 
I-beam in front and a 6-inch steel channel at the rear, held 2 
feet apart by a metal frame at each end. Each frame has two 
rollers 3 feet or more apart. These rollers rest on the side forms 
and permit the templet to be moved ahead easily and without 
jerks. Both beams are bent to the desired crown of the pave- 
ment. The lower flange of the I-beam is | to j^ inch lower than 
that of the channel. The space between the two beams is kept 
filled with dry 1 : 3 mortar, thoroughly mixed. As the templet is 
moved along, the I-beam shapes the fresh concrete accurately, 
and the channel leaves a thin, compacted bed of mortar on its 
surface, so that the bricks have a support which is true to grade 
in every respect. Experience shows that particular care must be 
taken in this type of construction to use concrete which will not 
flow but will quake. If it flows it will not support the bricks 
and if it does not quake it will be deficient in strength. The 
bricklaying should follow closely behind the templet before the 
concrete takes its initial set, and the workmen are required to 
move with special care over the bricks just laid. Some engineers 
require boards to be laid for the workmen to walk and stand on. 

Delivering and Laying Bricks 

In case the bricks are not tested at the plant, each carload 
must be sampled as it is delivered and the lot should not be 
allowed on the road until the samples have been tested and ap- 
proved. If this is not done, imperfect bricks are likely to find 
their way into the road, and the work of roadside inspection is 
made needlessly expensive and prolonged.^ 

1 Mr. Hinkle calls attention to the following paragraphs in the speci- 
fications of the Ohio State highway department: "If all the bricks in a 
shipment or in several shipments of the same make and kind of bricks 
appear to be uniform in quality two samples of 12 each may suffice. If 
in a shipment there appears to be different classes of bricks, such as bricks 
that appear to be more or less burned than others, a representative lot 
of 12 bricks is to be secured for each class of bricks, exclusive of the culls. 
The approximate number of each class sampled should be given on the 
notification card accompanying the samples. Unless otherwise ordered 
by the Engineer, at least one lot of samples should be taken for every 



BRICK ROADS 169 

Bricks are liable to considerable injury if handled roughly, 
and to prevent such injury to them after their acceptance by 
test many engineers specify the manner in which they shall be 
handled. The requirements of the Illinois highway department 
are as follows: 

Before the fine grading is finished, the bricks shall be hauled and neatly 
piled without the edging line in sufficient quantities to complete the brick 
su;rface. Clamps and conveyors may be used in connection with the 
work but the bricks shall not be dumped from industrial cars or vehicles, 
nor shall they be thrown to piles or to industrial cars or to vehicles. The 
bricks shall not be piled in any place where they will be likely to be be- 
splattered or covered with mud or otherwise injured. In delivering ^e 
bricks from the piles for placement in the pavement, no wheeling in bar- 
rows will be allowed oil the brick surface, but they shall be carried on 
pallets. They shall be placed upon the pallets so that when delivered to 
the dropper they will lie in such order that each brick in the regular oper- 
ation of placing it upon the foundation as prepared, will bring the lugs in 
the same direction with the best side uppermost. 

The bricks are laid with the best side up and the projections 
for spacing all in the same direction; in highway work they are 
laid in rows or courses at right angles to the curb. Alternate 
rows commence with a half brick at the curb and the joints in a 
row must be at least 3 inches from those in the row last laid. 
When the row reaches the curb towards which it is laid it must be 
completed with a bat at least 3 inches long. The fractured end 
of a broken brick must be toward the center of the road. Brick 
layers generally carry three or four rows across the roadway 
simultaneously, as this enables them to save considerable walk- 
ing. The bricks are laid from the bricks already in place, and 
no walking is permitted on the cushion or dry mortar bed. In 
order to keep the cross joints of uniform width, after about six 
or eight rows have been laid, a 4 x 4-inch timber 3 feet long is 
moved along the face of the last row and tapped lightly with a 
sledge. 

After the bricks are laid the surface is swept clean and inspected. 
The soft bricks are replaced by good ones; they are detected by 

100,000 bricks, care being taken to secure bricks from different parts oi 
the cars or piles so that the samples submitted will be representative of 
the bricks to be used. If at any time a shipment of bricks is received in 
which the quality of the bricks does not appear equal to that of the sam- 
ples previously submitted, additional samples should be immediately 
sent to the testing laboratory. A sufficient number of samples in ever^y 
case should be taken to insure the use of bricks of proper quality, but it 
should be borne in mind that the charges for transportation are high and 
only a sufficient number of samples should be submitted for test, which 
will permit of proper control of the quality of bricks used." 



170 



AMERICAN HIGHWAY ASSOCIATION 



Thousands of Bricks Required to Pave a Mile of Road of Different 
Widths with Different Numbers of Bricks per Square Yard 



BBICK PEB 






WIDTH OF STREET 






SQUARE 
















TAHD 


8 


10 


12 


15 


18 


20 


22 


33 


174.2 


193.6 


232.3 


290.4 


348.5 


387.2 


425.9 


34 


179.5 


199.5 


239.4 


299.2 


359.0 


398.9 


438.8 


35 


184.8 


205.3 


246.4 


308.0 


369.6 


410.7 


451.7 


36 


190.0 


211.2 


253.4 


316.8 


380.1 


422.4 


464.7 


37 


195.3 


217.1 


260.5 


325.6 


390.7 


434.2 


476.9 


38 


200.6 


222.9 


267.5 


334.4 


401.3 


445.9 


490.5 


39 


205.9 


228.8 


274.6 


343.2 


411.7 


457.6 


503.4 


40 


211.2 


234.7 


281.6 


352.0 


422.4 


469.4 


516.3 


41 


216.5 


240.5 


288.6 


360.8 


432.9 


481.1 


529.2 


42 


221.8 


246.4 


295.7 


369.6 


443.5 


492.8 


542.1 


43 


227.1 


252.3 


302.7 


378.4 


454.1 


504.6 


555.0 


44 


232.3 


258.1 


309.8 


387.2 


464.6 


516.3 


567.9 


45 


237.6 


264.0 


316.8 


396.0 


475.2 


528.0 


580.8 


46 


242.9 


269.9 


323.8 


404.8 


485.8 


539.8 


593.7 



dampening the surface of the road for they absorb moisture 
more quickly than the others. Bricks which are badly broken, 
spawled or misshaped are turned over or replaced by good ones, 
but slight chipping of the corners is not considered serious.^ 
The surface is then rolled, for which purpose a tandem self-pro- 
pelled roller weighing 2J to 4 tons is employed where a sand 
cushion is used and a hand roller about 2J feet long and 2J feet 
in diameter, weighing about 600 pounds, is preferred for mono- 
lithic pavements. The rolling should begin at one side of the 
road and proceed back and forth on lines slightly inclined toward 
the center of the roadway. When the center is reached the roller 
should be used on the other side of the road in the same way. 
Parts of the pavement which cannot be reached by the roller 
are rammed with a paver's tamper weighing about 50 pounds, 
the blows being struck on a 2-inch plank 10 to 12 inches wide 
and at least 6 feet long. 

After the rolling, the pavement is again inspected and any 
bricks which have been broken or seriously injured are replaced. 
The joints are examined, and if the sand-cushion has been forced 
up into them more than ^ inch in the sand-cushion type, the 
bricks are lifted out, the cushion reshaped, and the bricks relaid. 
This inspection of the joints is only necessary where a sand cushion 
is used. 

^ Mr. Hinkle considers that it is very desirable for all defective bricks 
to be culled out before the bricks are laid in the pavement. This will not 
only save the expense of replacing the defective bricks with good ones, 
but will avoid disturbing the cushion. This is more important with the 
monolithic than with other types of pavement. 



BRICK ROADS 



171 



Filling Joints 

Joints between the bricks are filled with sand, cement grout 
or bituminous material. Sand is objectionable because it gives 
very little support to the bricks, allows their edges to become 
chipped, and permits water to percolate down into the cushion. 
It is no longer employed except for roads for light travel, where 
the saving in first cost is considered more important than the 
probability that maintenance expenses will become high at an 
early date. 

Grout Fillers. — The grout filler is strongly advocated by many 
engineers on the ground that it holds the bricks firmly and does 



(Height 25" iMeiqhi;2l" 

.' { Depth of dox, .. { Depth of 
\W' i Wx,/4" 

\ 



{height, 29' 
\Deprh of Box, ,, 

^^^ /{Depth of 

'•ABox,I2" 




Box FOB Mixing Grout 



not wear away more rapidly than the vitrified clay. This claim 
rests upon the assumption that good grouting is done, for poor 
joints of this type are chipped out by horses' shoes and thus al- 
low the edges of the bricks to become broken. If the grouting 
Js properly done this will not happen.^ It is extremely im- 

^-Mr. Marr states: "The cement-grouted pavement seems to be the 
most satisfactory for country highways, and this has led us in our studies 
in Illinois to attach great importance to the perfection of the grout filler. 
We have been working along the line that, theoretically, the earth itself 
is the foundation for the pavement and is in itself wholly adequate, if it 
is thoroughly settled and properly drained. In other words, we hold that 
ordinary dry earth sustains any load which we place upon it while it is 



172 AMERICAN HIGHWAY ASSOCIATION 

portant, however, with cement filler that a rigid foundation be 
secured. 

Grout for filling joints should be made of equal parts of cement 
and clean, sharp, sand mixed thoroughly while dry. As a gen- 
eral rule, all of it should pass a No. 10 sieve but not more than 30 
per cent should pass a screen having 50 meshes to the inch. 
After the sand and cement are thoroughly mixed dry, water is 
added to bring the mass to a condition somewhat thinner than 
thin cream, so it will flow into the joints without any separation 
of its ingredients. The mixing is kept up continuously, either 
in a small batch mixer or the box shown in the accompanying 
illustration. The tendency on extensive work is to use a batch 
mixer equipped so it can be used for applying the grout. If the 
box is used, about 2 cubic feet of the dry mixture is made into 
mortar in each batch. The best grout is obtained when the 
water is added slowly. 

The surface of the pavement to be grouted is cleaned, well 
wet, and then covered with enough grout to about fill the 
joints. The grout is taken from the mixing box in scoops and 
after it is poured from them it is swept into the joints, usually 
with coarse rattan brooms. After a 50-foot section of road has 
had the joints filled in this manner, and before the grout first 
poured begins to set, a somewhat thicker grout is made and 
applied on the same surface. It is brushed into the joints with 
squeegees having rubber edges where they rest on the pavement. 
This process of applying the relatively thick grout and brushing 
it into the joints with squeegees is continued until the joints are 
completely filled. It is very desirable to apply the grout, so far 
as possible, to the exact parts of the pavement where it is to fill 
the joints. If any great excess of grout is applied at one place in 
the pavement and swept to another place, the cement and sand 
are liable to become separated and defective grout will result. 
If the bricks have rounded edges, the squeegees should be pressed 

in this condition, and that the real problem is to keep it in this condition 
by covering and waterproofing it with some material which will withstand 
the abrasive action of traffic. This, in turn, leads us to believe that if we 
use a thin base, such, for instance, as 2 inches of sand and cement mixed, 
or even 1 inch, or even, theoretically, i inch, the properly grouted bricks 
will then withstand successfully the action of any such traffic as we have 
at the present time. 

"The mortar bed has for its prime function the insurance of a perfect 
grout joint, by preventing earth or other foreign matter from working 
up into the bottom of the joints during construction. It has a secondary 
value in enabling us to obtain a smoother wearing surface by facilitating 
the proper grading of the bed on which the bricks lie by the use of mechan- 
ical methods such as templets. We have built a 6-mile stretch of brick 
road 9 feet wide, on a 1-inch mortar bed base, which 1 believe will demon- 
strate the correctness of the theory we are now holding." 



BRICK ROADS 



173 



firmly against them on the last brushing so that no thin edges 
of grout will remain on the surface, for they break away very 
soon and are liable to pull a part of the joint filler with them. 

To prevent the grout from flowing through the joints beyond 
the limits of the section where the filling is being done, strips of 
i^^ inch steel 6 inches wide and 3 feet long are inserted in the 
last transverse joint, to act as a dam until after the initial set of 
the cement. 

After the surface has been inspected, it is the practice in lUi- 
noip to cover it with sand, which is kept wet for ten days, and no 
travel is permitted on the road for three weeks after the grout 
has been poured. In Ohio and Pennsylvania, the sand is kept 
damp for at least five and four days respectively, and travel is 
kept off for at least ten days. In New York travel is kept off 
for ten days, and the covering must be kept moist for that period. 
The National Association of Paving Brick Manufacturers ad- 
vises keeping the covering wet for four days and travel off the 
road for fifteen days. 

Bituminous Fillers. — Bituminous fillers vary greatly in qual- 
ity, and the experience with some of the materials tried has not 
been satisfactory. The filler should not become soft during hot 
weather nor brittle during cold weather, it should adhere to the 
bricks, and it should not be injured by water. A 1 : 1 bituminous- 
sand mastic filler has recently been used considerably. Ob- 
viously climatic conditions should govern the selection of the 
material in some degree, for a filler suitable for the brick pave- 
ments of Florida might prove unsatisfactory during a New 
England winter. 

The Ohio State requirements for asphalt fillers are as follows : 

Specific gravity, 0.98 to 1.04. 

Solubility in chemically pure carbon disulphide, at least 99§ 
per cent. 

Matter soluble in 86°B. paraflSn naphtha, 25 to 40 per cent. 







Limits for penetration 




TEMPERATURE 


NEEDLE 


WEIGHT 


TIME 


PENETRATION 


25 

4 

46 


No. 2 
No. 2 
No. 2 


grams 

100 

200 

50 


5 sec. 
1 min. 
5 sec. 


2.5 to 5 mm. 
2 mm. or more 
10 mm. or less 



Melting point by cube method, 80°C. to 120°C. 
It shall be free from water and not foam when heated to 350°F. 
The Ohio State requirements for coal tar pitch fillers are as 
follows : 



174 AMERICAN HIGHWAY ASSOCIATION 

Specific gravity at 25°C., 1.23 to 1.3. 

Free carbon on extraction with carbon disulphide, 20 to 40 
per cent. 

Inorganic matter on ignition, 0.5 per cent. 

Melting point by cube method, 57°C. to 63°C. 

It shall be free from water and not foam when heated to 300°F. 

These bituminous fillers are used hot and the bricks should 
therefore be dry when the joints are poured. If a sand-cement 
bed is used, the water for it must be applied through the joints, 
if it is added in that way, long enough before the joints are filled 
to permit them to become dried out. 

The filler is melted in a kettle, from which it is usually drawn 
into funnel-shaped pourers terminating in a nozzle having an 
opening about J inch in diameter, with a valve by which the 
flow through it can be regulated. This is held over the joint, 
with the nozzle projecting into it, and carried along slowly. The 
joints are somewhat overfilled by the pourer, on the theory that 
the early travel on the pavement will force some of the surplus 
material into the joint and make it more dense. After the joint 
is poured, some engineers have it dusted over with sand, and it 
is customary to keep traffic off the pavement until the filler has 
cooled. 

A mixture of tar and sand, called a ''mastic filler," has been 
used to some extent. The hot tar and heated sand are mixed 
in equal volumes. A softer grade of tar is used in the mixture 
than that called for by the Ohio specification for a tar filler. 
This mastic filler is flushed into the joints by pouring it onto the 
pavement and spreading it with a squeegee. 

It is particularly desirable to roll the bricks and fill the joints to 
within at least 50 feet of the bricklaying work. If rain falls and 
the cushion becomes saturated, it is impossible to roll the bricks 
to a firm condition, for the wet sand allows them to rock and the 
cushion is forced up into the joints. By lifting out a brick here 
and there, the height of the sand in the joint can be seen and the 
character of the rolling judged from it. 

Expansion Joints 

In the early days of brick street pavements, the bricks at the 
crown of a street occasionally rose in summer as a result of the 
expansion of the pavement by heat. To remedy this, joints 
filled with some compressible material were laid along one or 
both curbs, and some engineers used similar transverse expan- 
sion joints at intervals of 50 to 75 feet. The longitudinal joints 
have proved useful, but there is some question as to the value of 
the transverse joints in street pavements. The objection to 
transverse joints is that they <ire worn away rather rapidly and 



BRICK ROADS 175 

this causes the travel to chip off the edges of the bricks separated 
by them. Whenever this chipping occurs to any extent, the 
pavement soon develops a rut or hole. Cracks in a country 
road, if properly filled when they first open and kept filled after- 
ward, do not injure it appreciably, and it is generally consid- 
ered that transverse joints in a brick wearing surface, to prevent 
transverse cracks, are more likely to cause than prevent trouble. 

Expansion joints are of two types, poured and prepared. The 
former are made by placing a board filler of the thickness of the 
joint against the curb and laying the bricks against it. The 
Maryland rule for the thickness of the joints is as follows: On 
streets 30 feet or more wide, IJ inches next each curb; on 20 to 
30-foot streets, 1 inch next each curb; on 12 to 20-foot streets, f inch 
next each curb; on streets under 12 feet, f inch next one curb. In 
Pennsylvania a f-inch joint at each curb is specified. On the 
Illinois brick roads with a sand-cement base a f-inch joint along 
one ciu*b is used. The plank filler usually consists of two thin 
6-inch boards of a wedge-shape cross-section, dressed on both 
sides. One of them is laid against the curb with the thin edge on 
the base, and the other is placed against it with the thick edge 
downward. The combined thickness of the two is equal to the 
thickness of the joint. Handles are attached to their upper 
edges, so they can be lifted out when the grout filler which has 
been poured has set. The filler for poured expansion joints should 
meet the requirements for the filler for other joints of this tj'pe. 
With the monolithic and sand-cement cushion types of pavement, 
the joints should be filled as far as the bricks are laid, each day. 

Prepared fillers are now extensively used. They are strips 
of bituminous material or some kind of felt or fabric impreg- 
nated with bitmninous material. They are placed against the 
curb and the bricks laid against them, thus doing away with the 
board fillers required with poured joints and making it unneces- 
sary to provide heating kettles on pavements with grouted 
joints. 

Experience on the Pennsylvania State highways has shown 
that a prepared filler extending the full depth of the brick some- 
times permitted water to penetrate from the road surface into 
the cushion, where it froze and heaved the bricks. It is there- 
fore considered advisable on that work to have the prepared 
filler stop from | to 1 inch below the surface of the road and to 
fill the top of the joint with hot bituminous material. 

Where a cement-sand bed is used, a f inch prepared expansion 
joint extending through the entire pavement is recommended 
by some engineers; it is placed in two strips, the first or bottom 
strip being placed in the concrete base, and the second strip im- 
mediately above it when the bed and bricks are laid. 



176 AMERICAN HIGHWAY ASSOCIATION 

Small Cubical Bricks 

Shortly after small stone blocks were introduced in Europe for 
constructing pavements having the trade name of *'Durax," the 
county superintendent of Monroe County, N. Y., J. Y. McClintock, 
employed cubes measuring 2 to 2| inches on a side for resurfacing 
old macadam roads to resist motor traffic. In 1916 he stated that 
vitrified clay cubes had given better results than those of other 
materials. Those laid in 1916 were 2| inches in each dimension, 
weighed about 1 pound each, and were laid 225 to the square 
yard. The only specification for the cubes is that they must not 
absorb more than 3 per cent, of their weight when immersed in 
water. They have been laid on a gravel base, broken slag, broken 
Btone and concrete, and the joints are filled with any local fine 
material. It is considered advisable to make the base several 
feet wider than the roadway, so that the gravel or broken stone 
shoulders adjacent to the cubes shall be supported rigidly and 
the tendency for the border cubes to become displaced will be 
minimized. 

Aspha-Bric 

During 1915 and 1916 attention was directed to the possibilities 
of asphalt impregnated brick. The idea of impregnating brick with 
bituminous material is not new. In 1893 brick boiled in coal tar 
were laid in Portland, Ore., and remained in service 17 years. 
A-bout 1907 nose brick boiled in asphalt were laid along the tracks 
of the Los Angeles Electric Railway Corporation and 2500 simi- 
lar brick were laid along tracks in San Francisco about 1912. 
Brick boiled in bituminous material have also been laid in Nash- 
ville and Chattanooga. 

The method of treating brick which came into prominence in 
1915 is designed to fill completely the pores in the brick. As the 
porosity of different grades and makes varies considerably, the 
quantity of impregnating material required will range from about 
6 to 15 per cent of the volume of the brick. As a result of the 
treatment it is claimed that the brick become impervious to mois- 
ture, the bituminous jointing material adheres more firmly to the 
treated than to the untreated brick, and the wearing properties, 
as indicated by the standard rattler test, are greatly improved. 
This last advantage is indicated in the accompanying tabulation 
of tests of untreated and treated ''second'^ brick conducted by 
Robert W. Hunt & Company. Each test was made with five 
untreated and five treated brick, 225 pounds of small shot and 75 
pounds of large shot, the rattler making 1800 revolutions at the 
rate of 30 revolutions per minute. The increase in wear due to 



BRICK ROADS 



177 



Results of itsts of untreated and asphalt impregnated brick. Each sample 
consisted of five untreated and five treated brick 



lAMPLO 


1 


2 


3 


4 


5 


6 

48.65 

51.33 

2.68 

11.88 
6.83 

24.42 
13.31 





7 

49.75 

54.60 

4.85 

19.57 
7.36 

39.34 
13.48 





8 


9 


Weight in pounds: 

Before treatment 

After treatment 

Asphalt used 

Loss in weight, pounds: 
Untreated 


50.66 

56.75 

6.09 

27.02 
8.38 

53.34 
14.77 

1 



48.81 

54.01 

5.20 

17.39 
8.96 

35.63 
16.59 





46.50 

48.97 

2.47 

28.81 
6.22 

61.96 
12.70 

3 
3 


53.35 

55.77 

2.42 

17.19 
10.07 

32.22 
18.06 


1 


45.25 

47.49 

2.24 

13.93 
6.51 

30.79 
13.71 





47.95 

49.94 

1.99 

13.63 
6.46 

28.43 
12.94 





50.03 

54.53 

4.50 

11 78 


Treated 


6.25 


Loss in weight, per 
cent: 
Untreated 


23.55 


Treated 


11.46 


Broken brick: 
Untreated 





Treated 










impregnation will, it is stated, enable manufacturers to stop their 
burning at a lower temperature than is now customary, thus 
materially reducing the number of poor brick in a kiln, and to 
obtain the necessary strength by impregnating the brick. It is 
also claimed that grades of brick unsuitable for pavements may 
be made into satisfactory pavers by impregnation. For example, 
impregnating clay building brick with 11.3 per cent of asphalt 
gave a product showing 9.3 per cent loss in the standard rattler 
test, although untreated brick showed 100 per cent loss after 500 
revolutions. Shale building brick which showed 42.4 per cent 
loss in the rattler test before they were treated, lost only 17 per 
cent after treatment. Sand-lime brick which showed 100 per 
cent loss after 400 revolutions lost only 23 per cent after being 
impregnated with 10 per cent of asphalt. Impregnating clay 
and shale building brick with 8| per cent of asphalt reduced the 
loss in the rattler test from 40.9 to 14.2 per cent. The impregna- 
tion of the brick also reduces their absorption of water to practi- 
cally nothing. 

The asphalt-impregnating process begins when the brick are 
removed from the kilns or dryers. They are loaded on small 
cars which are run into a cyUnder. There they are heated to 
about 300°F., which expands them, and a vacuum is produced 
in the cylinder to remove all moisture from the brick and leave 
their pores open. The cyhnder is then filled with a special grade 
of asphalt at a temperature of 350°F. and the cylinder put under 
heavy pressure until the gauges show that impregnation is com- 
plete. The asphalt is drained off and pressure again applied 
until the brick have cooled. During cooling they contract some- 
what, causing the asphalt to become sealed in the pores. 



A BRICK PAVEMENT ON A ONE-INCH CON- 
CRETE BASE^ 

A brick pavement was laid in 1917 in Stockland township, 
Iroquois County, Illinois, on a one-inch concrete base. This 
pavement is 9 feet wide, and the contract is for about 6J miles, 
of which about 3 miles has been constructed. The contract 
price for this work is approximately $8700 a mile, of which about 
$300 is for bridges and culverts and about $450 for grading. 
The price for the slab alone is $1.50 per square yard. 

This pavement is being laid on an old gravel road for a foun- 
dation and, in order to secure the full benefit of this old material, 
the gradient of the new pavement varies but slightly from that 
of the present road. By not disturbing the old gravel, it has 
been possible to secure a very firm subgrade and we have no doubt 
but the pavement will prove very satisfactory. The concrete 
base is composed of 1 part cement to 2J parts fine aggregate and 
4 parts coarse aggregate. The fine aggregate consists of sand 
all of which passes a |-inch mesh. The coarse aggregate con- 
sists of material which would be retained on a J-inch mesh and 
passes a J-inch mesh. As a matter of fact, there is very little 
of this material which will not pass a f inch mesh and it is the 
same type of gravel that is commonly used for roofing purposes. 

I have no doubt but this pavement would be practically as 
good as if the brick had been laid directly on the old gravel road, 
but in a construction of this kind, it is necessary to have some 
sort of a concrete base in order to secure a perfectly smooth and 
uniform surface on which to lay the bricks. 

The subgrade was thoroughly rolled and all soft places, of 
which there were very few, were removed and the subgrade 
brought up to a true plane by the addition of fresh material which 
was thoroughly compacted. Before concrete was placed, the 
subgrade was well wet; after the concrete was placed, it was 
struck off by means of a template and the bricks were laid di- 
rectly on the green concrete. 

Two brick setters were used on this job and by having a brick 
hammer on each side of the road, the setters not only started but 
finished the courses, as on a pavement of this width no bats, except 

^ By Rodney L. Bell, Division Engineer, Illinois State Highway De- 
partment. 

178 



BRICK PAVEMENT 179 

one half-sized brick, are required in starting and finishing the 
courses. Bricks were carried on to the pavement in such a way 
that the good side of the bricks was always placed up and the 
lugs all in one direction. By requiring the brick carriers to use 
some care, a large amount of the culling which ordinarily takes 
place on a brick road was eliminated. Just as soon as the bricks 
were culled, the pavement was swept and the rolling started. 

One man did nothing but keep the roller moving the entire 
time. It was a small hand roller about 30 inches in length and 
24 inches in diameter and when filled with water weighed about 
700 pounds. This weight was sufficient to secure a good surface 
over the entire length of the pavement. The first rolling was 
begun at the outer edge and the pavement was rolled parallel to 
the center line of the pavement. After the entire surface had 
been covered in this way, the pavement was cross-rolled in oppo- 
site directions, the roller making an angle of about 45 degrees 
with the center line of the pavement. 

In order to allow plenty of time to secure a thorough job of 
rolHng, the grouting machine was kept about 100 feet behind the 
brick layer. The grout mixture consisted of one part cement and 
1 part of sand mixed in a machine designed for this purpose. It 
was the intention to practically fill the joints at the first appli- 
cation so that after the grout had had a chance to settle, it would 
leave from § to f inch to be filled with subsequent applications. 

The second appUcation of the grout was mixed sUghtly thicker 
than the first, and was wheeled back over the pavement from the 
mixing machine rather than bother with moving the machine 
back over the pavement a second time. This application was 
worked into the joints by use of a squeegee and on the final going 
over, the squeegees were pulled at an angle of about 45 degrees 
with the joints in order to secure a better surface and to keep 
the grout from being dragged out from between the brick. 

After the grout had set sufficiently, the pavement was covered 
with 1 inch of loose dirt, which was kept wet for one week. The 
pavement was opened to traffic after it had been down three 
weeks. 

This work is being paid for by a bond issue which has been 
voted by Stockland township, Iroquois County, and is under 
the general supervision of Benj. Jordan, county superintendent 
of highways of Iroquois County. 



HIGHWAY BONDS^ 

The mathematical theory of interest as applied to bond cal- 
culations is explained in a section of Bulletin 136 of the United 
States Department of Agriculture which has tables of much 
value to those making a detailed examination of the subject. 
For the usual purposes of highway officials, however, the much 
simpler tables which are printed herewith are not only sufficient 
in scope but also more easily used. 

The bonds used almost universally until a few years ago were 
of the sinking-fund type. Parties issuing them have to provide 
annually during the term of the bonds the stipulated interest 
and, theoretically, set aside a sum at interest which will amount 
at the end of the term to the principal of the bonds. This an- 
nual sum set aside at interest is called the sinking fund, and the 
amount which must be raised for such a fund depends upon the 
interest it bears. This interest is usually quite low in comparison 
with the interest paid on the bonds. 

Unfortunately the financial methods of public officials do not 
always remain above criticism and it often happens that the annual 
payment into the sinking fund is forgotten or neglected.^ Some- 
times the money accumulated in the sinking fund is diverted 
from its purpose. Such departures from sound finance result in 
a lack of money to pay off the bonds when they become due, as 
agreed, and it then becomes necessary to issue a new series of 
bonds to carry this indebtedness. This is a serious matter when 
the improvements for which the bonds were issued have become of no 
further use, as in the possible case of a worn-out road surface, 
or obsolescent, as in the possible case of an overloaded bridge, 
when the taxpayers who contribute for the second bond issue are 
obliged to pay for something for which they receive Httle or no 
benefit. This is not equitable, and so some states fix the term 
of bonds which may be issued to pay for certain classes of im- 

^ Revised by B, K. Coghlan, associate professor of highway engineer- 
ing, Agricultural and Mechanical College of Texas. 

* Baker, Watts & Co., bankers, of Baltimore, make the tollowing com- 
ment: "We view it as a very serious matter to neglect the sinking fund, 
regardless of the character of the improvement for which the bonds are 
issued. We think that public ofl&cials cannot be too forcibly impressed 
with the absolute necessity of managing public funds strictly in accordance 
with the laws and ordinances authorizing bond issues, and any neglect or 
diversion of public sinking funds should be summarily dealt with." 

180 



HIGHWAY BONDS 181 

provements. In New Jersey, for example, the term of bonds for 
gravel roads is limited to five years, waterbound or bituminous 
macadam ten years, bituminous concrete fifteen years, 6-inch 
concrete twenty years, block pavements twenty years, sheet 
asphalt on a concrete base twenty years, and stone, concrete 
and iron bridges thirty years. The useful life of the improve- 
ment is what must be considered, and this is determined in some 
cases by obsolescence rather than depreciation, notably in the 
case of bridges. The attractiveness of bonds for road work 
would be enhanced in many cases if an equivalent of the fol- 
lowing statute, in force in Mississippi, were generally adopted: 

The public highway or highwaj's so surveyed and adopted by such com- 
missioners shall be constructed and maintained out of the proceeds of 
such bonds; proceeds of such bonds to be used alone in their construction; 
and the board of supervisors shall levy an annual tax, on the recommen- 
dation of such commissioners, on all the taxable property in such district 
or districts of not exceeding 1 mill on the dollar, which shall be used to 
supplement the general fund of the county in maintaining said road or 
roads and the culverts, bridges and levees thereon. 

The importance of maintenance of roads is so great that 
statutes authorizing bond issues for construction should require, 
as part of the stipulations under which the bonds are issued, an 
adequate financial provision for the upkeep of the roads during 
the term of the bonds. This insures a full statement of the 
financial obligations of the bond issue upon the taxpayers before 
they vote on the issue. 

The investment of the sinking fund affords an indication of 
the financial ability of a community. In some sections of the 
country, the investment is intrusted to special boards of sinking 
fund commissioners, and appointment to such a board is re- 
garded as a high honor, so that the positions are filled by men of 
the highest business standing. In such cases the community 
not only feels confident of its financial stability but its bond 
issues are sought so eagerly that it is not necessary to pay high 
rates of interest. In a few places, sinking funds have been 
neglected and the financial standing of the community suffers 
in consequence. 

A second type of bond is known as the annuity bond. An 
annuity is a fixed sum paid at regular intervals of time for either 
a definite term or for the life of the beneficiary of the annuity. 
An annuity bond draws interest at an agreed rate, but at the 
close of each retirement period stated in the bond, the payment 
to the bondholders includes both the interest that has accrued 
during the period since the last payment and enough of the 
principal to make the fuU payment a definite, uniform amount 
at the close of each retirement period. The annual payment at 



182 AMERICAN HIGHWAY ASSOCIATION 

the end of the first retirement period is mainly for interest and 
that at the end of the last period is mainly for retiring the last 
of the outstanding principal. The advantage of the plan is that 
it retires some principal annually and thus saves the taxpayer 
the expense of paying interest on the whole of a bond issue dur- 
ing its term. This makes annuity bonds less expensive than 
sinking fund bonds to the county issuing them. 

The annuity bond issue possesses the advantage of requiring 
the same amount to be raised each year, during its term. The 
annual payments must be adjusted, however, so that the amount 
of principal retired will be some multiple of SlOO, $500 or $1000, 
or whatever sum is the face value of one bond. Consequently the 
actual payment on annuity issues at the end of a retirement period 
is not the uniform theoretical amount given in bond tables but 
an amount varying slightly from it, sometimes more and some- 
times less.^ 

The serial bond issue is a type which has found favor with both 
borrowers and lenders. The farmer finds it desirable because it 
retires each year a part of the principal, and is thus more econom- 
ical than a sinking fund bond issue. The purchasers of the bonds 
like them because there is a strong pubhc sentiment in favor of 
serial bonds, which gives them standing as a good type of invest- 
ment security. It is the least expensive method of borrowing 
money by issuing bonds, as an examination of the accompanying 
tables will show. 

One defect of serial bonds for certain classes of pubUc im- 
provements is that the heaviest payments for interest and the 
retirement of principal must be made in the early years of the 
term of the bonds, before the work for which they pay has yielded 
any returns. Consequently what are known as deferred serial 
bonds are now used to meet such conditions as often arise in 
road districts. With such a type of bond, no principal is retired 
until a certain period, usually five years, has elapsed. During 
this period interest is paid but nothing more. Thereafter the 
principal is retired by uniform amounts and the interest charges 
are met just as in the case of straight serial bonds having a term 
shorter by five years, or whatever is the deferred period. In 
this way a road district need not pay anything but interest until 

* The following comment on this type of bond has been received from 
John S. Harris, of the banking house of Sidney Spitzer and Company, 
Toledo: "We would not suggest your recommending the installment 
(annuity) bonds, as they are very hard to figure and hard to dispose of. 
It is necessiiry to figure each year when you collect your coupons the 
amount of principal and the amount of interest. A serial bond answers 
the same purpose and is much more attractive to the investing public. 
Road bonds should not be issued in any other way than as serial bonds, as 
every one knows that issuing long-time road bonds is wrong." 



HIGHWAY BONDS 183 

the improvements have begun to yield a return and it need not 
pay so much for the use of money as when it issues sinking fund 
bonds. 

The question which taxpayers generally put to public officials 
regarding a bond issue is what increase such an issue will make in 
the annual taxes. A series of examples will show how the ac- 
companying tables can be used to answer such questions. 

What is the tax rate for a $300,000 issue of 5 per cent, 40-year 
bonds, retired by a sinking fund drawing 3 per cent, when the 
tax valuation of the road district is $9,300,000? 

The table of the annual cost of sinking fund bonds shows that the 
annual cost of a $1 bond of this class is 6.326 cents. The annual 
cost of a $300,000 issue will be $18,978. The additional tax per 
$100 valuation in the district will be $18,978 -^ 93,000 = 20.407 
cents. Any taxpayer can find out what his additional tax will 
be by multiplying 20.407 cents by the number of hundreds of 
dollars worth of property for which he is assessed. If his prop- 
erty is assessed at $2000, for example, his additional tax for 
roads will be $4.08. 

How much money would be saved by issuing annuity rather 
than sinking fund bonds in this case? 

The annual cost of a 1-dollar 4-per cent, 40-year annuity bond 
is shown by the table to be 5.828 cents, so the annual cost of a 
$300,000 issue will be $17,484. The additional tax per $100 
valuation will be 18.8 cents, or 1.607 cents less than under the 
sinking fund system. The man whose property is assessed at 
$2000 would save 32 cents, and the district as a whole would 
save $1494.51, which would go a long ways toward paying for 
the engineering expenses of the road improvement. 

What is the least expensive type of a $300,000 issue of 5 per 
cent, 40-year bonds to the above district? 

The four accompanying tables show that the straight serial 
bond is the least expensive type, for the average annual cost of 
a 1-dollar bond of this type is 5.062 cents. This is equivalent 
to $15,186 for a $300,000 issue. The additional tax per $100 
valuation will be 16.329 cents, 4.978 cents less than under the 
sinking fund type, which will save 81 cents to the man having 
property assessed at $2000. The saving to the district will be 
$3792 as compared with a sinking fund issue and $2298 as com- 
pared with an annuity issue. 

The drawback of a straight serial bond can be seen from the fig- 
ures of the payment needed at the end of the first and the fortieth 
years, 7.5 and 2.625 cents respectively on a 1-dollar bond. Road 
improvements do not yield any benefits until completed, and by 
deferring payment on the principal for five years, the additional 
cost to the community will average only $939 a year. The 
maximum annual amount will be somewhat higher than in a 



184 AMERICAN HIGHWAY ASSOCIATION 

straight 40-year serial issue, because the principal must be re- 
tired in 35 years instead of 40 years, but this disadvantage may 
not outweigh the desirabihty of deferring the repayment of the 
principal. 

The management of a bond issue requires attention to all the 
requirements of the laws governing such matters and a knowledge 
of the conditions which affect the value of bonds. Every step 
which the law requires to be taken in connection with such bonds 
must not only be taken properly but recorded fully and clearly. 
As soon as the voters authorize the issue, a statement of the fact 
should be drawn up, showing also the area, population and as- 
sessed valuation of the district, the value of its agricultural and 
industrial products, its material resources and the extent of their 
development, the banking and transportation facilities serving 
it, the existing indebtedness of the district, the condition and 
number of the schools, and all other information which will indi- 
cate the resources and character of the community that has de- 
cided to borrow the money. This information should be sent 
to banking houses and insurance companies making a specialty 
of purchasing public bonds and, if the issue is a large one, it 
should be advertised in financial journals. There should be 
ample time between the pubhcation of these notices and the sale 
of the bonds for purchasers to make a full investigation of them. 

^ Private sales of bonds for pubUc works should be discouraged 
all sales of bonds should be publicly advertised, and bidders 
should be invited to submit sealed bids on or before a certain 
date. The bonds should be sold to the highest responsible bid- 
der who complies with all of the terms and conditions of the sale. 
The city or county should reserve the right to reject any or all 
of the bids, as a protection against any effort to pool bids and 
purchase the bonds at a price considerably less than their value. 

Some cities and counties engage competent attorneys, famiUar 
with the preparation of the legal papers pertaining to bond is- 
sues, to examine the records prior to the sale and to prepare all 
necessary forms. The city or county assumes the expense for 
all such work and furnishes the successful bidder with the approv- 
ing opinion of the counsel thus engaged and with the executed 
bonds. Some cities and counties go even further by providing 
imiform proposal blanks for the bonds and refusing to accept bids 
not made on such blank. The advantage of these provisions is 
that the seller knows he is offering a legally and vahdly issued 
bond, the buyer has the same assurance, and the value of the is- 
sue is certainly enhanced thereby. The seller is undoubtedly re- 
imbursed for the expense incurred in such preparatory work by 
the price he receives for the bonds. 

^This and the next paragraph were prepared by Baker, Watts & 
Company. 



Annual cost of a 1-dollar sinking-fund bond for different terms, interest 
rates and rates of interest on sinking fund 



INTBB- 




RATE OF INTEREST ON BONDS, PER CENT 


B8T ON 










SINK- 
ING 


TERM 


4 


4.25 


4.5 


4.75 


5 


5.25 


5.5 


ft 


FUND 




















percent 


years 


cents 


cents 


cents 


cents 


cents 


cents 


cents 


cents 


2 


5 


23.216 


23.466 


23.716 


23.966 


24 . 216 


24.406 


24.716 


25.216 




10 


13.133 


13.383 


13.633 


13.883 


14.133 


14.383 


14.633 


15.133 




15 


9.783 


10.033 


10.283 


10.533 


10.783 


11.033 


11.283 


11.783 




20 


8.116 


8.366 


8.616 


8.866 


9.116 


9.366 


9.616 


10.116 




25 


7.122 


7.372 


7.622 


7.872 


8.122 


8.372 


8.622 


9.122 




30 


6.465 


6.715 


6.965 


7.215 


7.465 


7.715 


7.965 


8.465 




35 


6.000 


6.250 


6.500 


6.750 


7.000 


7.250 


7.500 


8.000 




40 


5.656 


5.906 


6.156 


6.406 


6.656 


6.906 


7.156 


7.656 




45 


5.391 


5.641 


5.891 


6.141 


6.391 


6.641 


6.891 


7.391 




50 


5.182 


5.432 


5.682 


5.932 


6.182 


6.432 


6.682 


7.182 


2.5 


5 


23.023 


23.273 


23.523 


23.773 


24.023 


24.273 


24.523 


25.023 




10 


12.926 


13.176 


13 . 426 


13.676 


13.926 


14.176 


14.426 


14.926 




15 


9.577 


9.827 


10.077 


10.327 


10.577 


10.827 


11.077 


11.577 




20 


7.915 


8.165 


8.415 


8.665 


8.915 


9.165 


9.415 


9.915 




25 


6.928 


7.178 


7.428 


7.678 


7.928 


8.178 


8.428 


8.928 




30 


6.278 


6.528 


6.778 


7.028 


7.278 


7.528 


7.778 


8.278 




35 


5.821 


6.071 


6.321 


6.571 


6.821 


7.071 


7.321 


7.821 




40 


5.484 


5.734 


5.984 


6.234 


6.484 


6.734 


6.984 


7.484 




45 


5.227 


5.477 


5.727 


5.977 


6.227 


6.477 


6.727 


7.227 




50 


5.026 


5.276 


5.526 


5.776 


6.026 


6.276 


6.526 


7.026 


3 


5 


28.835 


23.085 


23.335 


23.585 


23.835 


24.085 


24.335 


24.835 




10 


12.723 


12.973 


13.223 


13.473 


13.723 


13.973 


14.223 


14.723 




15 


9.377 


9.627 


9.877 


10.127 


10.377 


10.627 


10.877 


11.377 




20 


7.722 


7.972 


8.222 


8.472 


8.722 


8.972 


9.222 


9.722 




25 


6.743 


6.993 


7.243 


7.493 


7.743 


7.993 


8.243 


8.743 




30 


6.102 


6.352 


6.602 


6.852 


7.102 


7.352 


7.602 


8.102 




35 


5.654 


5.904 


6.154 


6.404 


6.654 


6.904 


7.154 


7.654 




40 


5.326 


5.576 


5.826 


6.076 


6.326 


6.576 


6.826 


7.326 




45 


5.079 


5.329 


5.579 


5.829 


6.079 


6.329 


6.579 


7.079 




50 


4.887 


5.137 


5.387 


5.637 


5.887 


6.137 


6.387 


6.887 


3.5 


5 


22.648 


22.898 


23.148 


23.398 


23.648 


23.898 


24.148 


24.648 




10 


12.524 


12.774 


13.024 


13.274 


13.524 


13.774 


14.024 


14.524 




15 


9.183 


9.433 


9.683 


9.933 


10.183 


10.433 


10.683 


11.183 




20 


7.536 


7.786 


8.036 


8.286 


8.536 


8.786 


9.036 


9.536 




25 


6.567 


6.817 


7.067 


7.317 


7.567 


7.817 


8.067 


8.567 




30 


5.937 


6.187 


6.437 


6.687 


6.937 


7.187 


7.437 


7.937 




35 


5.500 


5.750 


6.000 


6.250 


6.500 


6.750 


7.000 


7.500 




40 


5.183 


5.433 


5.683 


5.933 


6.183 


6.433 


6.683 


7.183 




45 


4.945 


5.195 


5.445 


5.695 


5.945 


6.195 


6.445 


6.945 




50 


4.763 


5.013 


5.203 


5.513 


5.763 


6.013 


6.263 


6.763 


4 


5 


22.463 


22.713 


22.963 


23.213 


23.463 


23.713 


23.963 


24.463 




10 


12.329 


12.579 


12.829 


13.079 


13.329 


13.579 


13.829 


14.329 




15 


8.994 


9.244 


9.494 


9.744 


9.994 


10.244 


10.494 


10.994 




20 


7.358 


7.608 


7.858 


8.108 


8.358 


8.608 


8.858 


9.358 




25 


6.401 


6.651 


0.901 


7.151 


7.401 


7.651 


7.901 


8.401 




30 


5.783 


6.033 


6.283 


6.533 


6.783 


7.033 


7.283 


7.783 




35 


5.358 


5.608 


5.858 


6.108 


6.358 


6.608 


6.858 


7.358 




40 


5.052 


5.302 


5.552 


5.802 


6.052 


6.302 


6.552 


7.052 




45 


4.826 


5.076 


5.326 


5.576 


5.826 


6.070 


6.326 


6.826 




50 


4.655 


4.905 


5.155 


5.405 


5,655 


5.905 


6.155 


6.655 



185 



186 



AMERICAN HIGHWAY ASSOCIATION 



Annual cost of a 1 -dollar sinking-fund bond for different terms, interest 
rates and rates of interest on sinking fund — Continued 



INTER- 






RATE OF INTEREST ON BONDS. PER CENT 




EST ON 


TERM 
















SINK- 


















ING 
FUND 




4 


4.25 


4.5 


4.75 


5 


5.25 


5.5 


6 


per cent 


years 


cents 


cents 


cents 


cents 


cents 


cents 


cents 


cents 


4.5 


5 


22.279 


22.529 


22.779 


23.029 


23.279 


23.529 


23.779 


24.279 




10 


12.138 


12.388 


12.638 


12.888 


13.138 


13.388 


13.638 


14.138 




15 


8.811 


9.061 


9.311 


9.561 


9.811 


10.061 


10.311 


10.811 




20 


7.188 


7.438 


7.688 


7.938 


8.188 


8.438 


8.688 


9.188 




25 


6.244 


6.494 


6.744 


6.994 


7.244 


7.494 


7.744 


8.244 




30 


5.639 


5.889 


6.139 


6.389 


6.639 


6.889 


7.139 


7.639 




35 


5.227 


5.477 


5.727 


5.977 


6.227 


6.477 


6.727 


7.227 




40 


4.934 


5.184 


5.434 


5.684 


5.934 


6.184 


6.434 


6.934 




45 


4.720 


4.970 


5.220 


5.470 


5.720 


5.970 


6.220 


6.720 




50 


4.560 


4.810 


5.060 


5.310 


5.560 


5.810 


6.060 


6.560 



Annual cost of a 1 -dollar annuity bond for different terms and rates of interest 









EATB OF 


INTEREST ON BONDS, 


PER CENT 






TIERM 




















4 


4.26 


4.5 


4.75 


5 


5.25 


5.5 


6 


teart 


centi 


cents 


cents 


cents 


cents 


cents 


cents 


cents 


5 


22.462 


22.621 


22.779 


22.938 


23.097 


23.257 


23.418 


23.740 


10 


12.329 


12.483 


12.638 


12.794 


12.950 


13.108 


13.267 


13.587 


15 


8.994 


9.152 


9.311 


9.472 


9.634 


9.798 


9.963 


10.296 


20 


7.358 


7.522 


7.688 


7.855 


8.024 


8.195 


8.368 


8.718 


25 


6.401 


6.571 


6.744 


6.919 


7.095 


7.274 


7.455 


7.823 


30 


5.783 


5.960 


6.139 


6.321 


6.505 


6.692 


6.880 


7.265 


35 


5.358 


5.541 


5.727 


5.916 


6.107 


6.301 


6.497 


6.897 


40 


5.052 


5.242 


5.434 


5.630 


5.828 


6.029 


6.232 


6.646 


45 


4.826 


5.022 


5.220 


5.422 


5.626 


5.833 


6.043 


6.470 


50 


4.655 


4.856 


5.060 


5.267 


5.478 


5.691 


5.906 


6.344 



HIGHWAY BONDS 



187 



Variations in annual cost of a 1 -dollar serial bond for different terms and 
rates of interest, the principal being retired by the same amount at the 

end of each year 



years 

5 



10 



15 



20 



25 



30 



35 



40 



45 



50 



PAYMENT 



date 

First year 
Last year. 
Average... 

First year 
Last year. 
Average... 

First year 
Last year. 
Average... 

First year 
Last year. 
Average... 

First year 
Last year. 
Average... 

First year 
Last year. 
Average... 

First year 
Last year. 
Average... 

First year 
Last year. 
Average... 

First year 
Last year. 
Average... 

First year 
Last year. 
Average... 



RATE OF INTEREST, PER CENT 



cents 

24.000 
20.800 
22.400 

14.000 
10.400 
12.200 

10.667 
6.933 
8.800 

.9.000 
5.200 
7.100 

8.000 
4.160 
6.080 

7.333 
3.467 
5.400 

6.857 
2.971 
4.914 

6.600 
2.600 
4.550 

6.222 
6.311 
4.267 

6.000 
2.080 
4.040 



4.25 



cents 

24.250 
20.850 
22.550 

14.250 
10.425 
12.337 

10.917 
6.950 
8.933 

9.250 
5.213 
7.231 

8.250 
4.170 
6.210 

7.583 
3.475 
5.530 

7.107 
2.978 
5.047 

6.750 
2.606 
4.678 

6.472 
3.316 
4.394 

6.250 
2.085 
4.167 



4.6 4 75 



cents 

24.500 
20.900 
22.700 

14.500 
10.450 
12.475 

11.167 
6.967 
9.067 

9.500 
5.225 
7.362 

8.500 
4.180 
6.340 

7.833 
3.483 
5.658 

7.357 
2.985 
5.171 

7.000 
2.613 
4.806 

6.722 
2.322 
4.522 

6.500 
2.090 
4.295 



cents 

24.725 
20.950 
22.850 

14.750 
10.475 
12.613 

11.^17 
6.984 
9 200 

9.750 
5.238 
7.494 

8.750 
4.190 
6.470 

8.083 
3.491 

5.787 

7.607 
2.993 
5.300 

7.250 
2.619 
4.934 

6.972 
2.328 
4.650 

6.750 
2.095 
4.427 



cents 

25.000 
21.000 
23.000 

15.000 
10.500 
12.750 

11.667 
7.000 
9.333 

10.000 
5.250 
7.625 

9.000 
4.200 
6.600 

8.333 
3.500 
5.916 

7.857 
3.000 
5.428 

7.500 
2.625 
5.062 

7.222 
2.333 

4.777 

8.000 
2.100 
4.550 



6.25 



cents 

25.250 
21.050 
23.150 

15.250 
10.525 

12.888 

11.917 

7.017 
9.467 

10.250 
5.263 
7.756 

9.250 
4.210 
6.730 

8.583 
3.509 
6.046 

8.107 
3.007 
5.557 

7.750 
2.632 
5.191 

7.472 
2.339 
4.905 

7.250 
2.105 
4.677 



5.5 



cents 

25.500 
21 . 100 
23.300 

15.500 
10.550 
13.025 

12.167 
7.034 
9.600 

10.500 
5.275 

7.887 

9.500 
4.220 
6.810 

8.833 
3.517 
6.175 

8.357 
3.014 

5.685 

8.000 
2.640 
5.320 

7.722 
2.344 
5.033 

7.500 
2.110 
4.805 



cents 

26.000 
21.200 
23.600 

16.000 
10.600 
13.300 

12.667 
7.067 
9.867 

11.000 
5.287 
8.144 

10.000 
4.240 
7.120 

9.333 
3.535 
6.434 

8.857 
3.028 
5.942 

8.500 
2.654 
5.577 

8.222 
2.355 
5.288 

8.000 
2.120 
5.060 



188 



AMERICAN HIGHWAY ASSOCIATION 



Variations in annual cost of a 1 -dollar deferred serial bond for different 
terms and rates of interest, the principal being retired by the same amount 
at the end of each year beginning with the end of the sixth year 



years 

10 



15 



20 



25 



30 



35 



40 



45 



50 



PAYMENT 



date 

1-5 years... 
Sixth year. 
Last year.. 
Average.... 

1-5 years... 
Sixth year. 
Last year.. 
Average 

1-5 years... 
Sixth year. 
Last year. . 
Average — 

1-5 years... 
Sixth year. 
Last year. . 
Average — 

1-5 years... 
Sixth year. 
Last year. . 
Average.... 

1-5 years... 
Sixth year. 
Last year. . 
Average 

1-5 years... 
Sixth year. 
Last year. . 
Average — 

1-5 years... 
Sixth year. 
Last year. . 
Average 

1-5 years... 
Sixth year. 
Last year. , 
Average 



BATE OP INTEREST, PEB CENT 



cents 

4.000 
24.000 
20.800 
13.200 

4.000 
14.000 
10.400 

9.467 

4.000 

10.667 

6.933 

7.600 

4.000 

9.000 

5.200 

.6.480 

4.000 
8.000 
4.160 
5.733 

4.000 
7.333 
3.467 
5.200 

4.000 
6.857 
2.971 
4.800 

4.000 
6.500 
2.600 
4.489 

4.000 
6.222 
2.311 
4.240 



4.25 



cents 

4.250 
24.250 
20.850 
13.400 

4.250 
14.250 
10.425 

9.641 

4.250 

10.917 

6.950 

7.762 

4.250 

9.250 
5.213 
6.635 

4.250 
8.250 
4.170 
5.883 

4.250 
7.583 
3.475 
5.347 

4.250 
7.107 
2.978 
4.947 

4.250 
6.750 
2. 
4. 



4.6 



606 
630 



4.250 
6.472 
2.316 
4.380 



cents 

4.500 
24.500 
20.900 
13.600 

4.500 
14.500 
10.450 

9.817 

4.500 

11.167 

6.967 

7.925 

4.500 
9.500 
5.225 
6.790 

4.500 
8.500 
4.180 
6.033 

4.500 
7.833 
3.483 
5.492 

4.500 
7.357 
2.985 
5.087 

4.500 
7.000 
2.613 
4.772 

4.500 
6.722 
2.322 
4.720 



4.75 



cents 

4.750 
24.725 
20.950 
13.800 

4.750 
14.750 
10.475 

9.992 

4.750 

11.417 

6.984 

8.088 

4.750 
9.750 
5.238 
6.945 

4.750 
8.750 
4.190 
6.183 

4.750 
8.083 
3.491 
5.639 



750 
607 
993 
231 



cents 

5.000 
25.000 
21.000 
14.000 

5.000 
15.000 
10.500 
10.166 

5.000 

11.667 

7.000 

8.250 

5.000 

10.000 

5.250 

7.100 

5.000 
9.000 
4.200 
6.333 

5.000 
8.333 
3.500 

5.785 

5.000 
7.857 
3.000 
5.375 



4.750 
7.250 
2.619 
4.914 

4.750 
6.972 
2.328 
4.385 



5.25 



000 
500 
625 
055 



5.000 
7.222 
2.333 
4.799 



cents 

5.250 
25.250 
21.050 
14.275 

5.250 
15.250 
10.525 
10.342 

5.250 

11.917 

7.017 

8.413 

5.250 

10.250 

5.263 

7.255 

5.250 
9.250 
4.210 
6.483 

5.250 
8.583 
3.509 
5.932 

5.250 
8.107 
3.007 
5.519 

5.250 
7.750 
2.632 
5.198 

5.250 
7.472 
2.339 
4.415 



5.5 



cents 

5.500 
25.500 
21.100 
14.400 

5.500 
15.500 
10.550 
10.516 

5.500 

12.167 

7.034 

8.575 

5.500 

10.500 

5.275 

7.410 

5.500 
9.500 
4.220 
6.592 

5.500 
8.833 
3.517 
6.079 

5.500 
8.357 
3.014 
5.662 

5.500 
8.000 
2.640 
5.340 

5.500 
7.722 
2.344 
4.530 



cents 

6.000 
26.000 
21.200 
14.800 

6.000 
16.000 
10.600 
10.867 

6.000 

12.667 

7.067 

8.900 

6.000 

11.000 

5.287 

7.715 

6.000 

10.000 

4.240 

5.933 

6.000 
9.333 
3.535 
6.372 

6.000 
8.857 
3.028 
5.199 

6.000 
8.500 
2.654 
5.624 

6.000 
8.222 
2.355 
4.759 



RESISTANCE OF ROADS TO TRACTION 

The resistance to traction of a small number of pavements of 
different types, in different conditions was investigated in 1915 
by the electrical engineering department of the Massachusetts 
Institute of Technology. A half-ton electric delivery wagon was 
used, and each test was made by driving the wagon over the test 
pavement in one direction and then in the other, so that the ef- 
fect of the wind, if any, would be neutralized by averaging the 
results of the runs in both directions. The tests are described in 
a paper presented to the American Institute of Electrical Engi- 
neers in June, 1916, by Profs. A. E. Kennelly and O. R. Schmg. 
The results were summarized in the accompanying illustration. 

Curve 1 is nearly flat, and the authors state that if the effect 
of air resistance was eliminated from the total resistance to trac- 
tion, the resistance of a good level asphalt pavement would be 
about 17 pounds per ton at all speeds. Such a pavement in 
poor condition had a resistance of about 23 pounds per ton when 
the wagon ran at 12 miles per hour and 25 pounds at 15 miles. 
There were no tests of wood block pavements in poor condition ; 
curve 2 gives the results for a good pavement. 

Curve 3 is for a good brick pavement; the effect of slight wear 
of bricks was to increase the tractive resistance to 25 pounds per 
ton at 12 miles and about 30 pounds at 15 miles. 

Curve 4 is for a dry, hard water-bound macadam road in fair 
condition. A similar road in a dusty condition showed an in- 
crease of 3 pounds in the resistance to traction at all speeds. A 
poor, damp road in poor condition offered a resistance of 33 
pounds at 10 miles and 39 pounds at 13 miles. Oiling a good 
water-bound macadam road increased its resistance to traction 
about 5 pounds, this increase gradually growing larger as the 
speed increased. 

Curve 5 is for bituminous macadam in good condition. The 
curve for another road in good condition began with a resistance 
of a little under 26 pounds per ton at 9 miles an hour and in- 
creased to 32 pounds at 14 miles. An old road of this type in 
poorly patched -condition offered a resistance of about 29 pounds 
at 8 miles and 37 pounds at 13 miles. A good road which was 
recently treated and still soft had a resistance of 33 pounds at 8 
miles and nearly 36 pounds at 13 miles, as shown in Curve 9. 
A very poor, soft road with many holes had a resistance of 41 

189 



190 



AMERICAN HIGHWAY ASSOCIATION 



pounds at 7 miles and 54 pounds at 12 miles, showing what a 
rapid increase to resistance follows an attempt to go at even 
moderate speed over such a road. 

The authors make the following comments of the tests: 
There are three principal elements which determine the trac- 
tive-resistance curve for different speeds and a given vehicle, within 
the range of conditions covered by the tests. 

The first element is a constant resistance, the magnitude of 
which depends on the lack of resihence of the road surface and 
the tires, that is to say, on the energy losses due to displacement 
of tire material and road-surface material. This constant ele- 




10 20 



i 



16 18 20 22 

SPEED- KM. PER HR. 
I I t • t 
10 11 12 13 14 

SPEED -MILES PER HR 



24 
l'5 



16 



Curves Showing Resistance to Traction at Different Speeds 

ment would be encountered upon a smooth, level road of the 
particular type considered, in the absence of impact, air and wind 
resistance. 

The second element is an increasing resistance with increasing 
speed due to impact losses. This resistance results from lack of 
smoothness of the road surface and varies approximately as the 
second power of the velocity at impact. 

The third element is an increasing resistance with increased 
speed. It is due to the air pressure against the front of the 
vehicle and varies approximately as the second power of the 
speed. 



RESISTANCE OF ROADS TO TRACTION 191 

The first element is called the displacement resistance, the second 
the impact resistance and the third the air resistance. The 
displacement resistance is very marked in Curve 10, for a granite- 
block pavement with sand joints. The displacement resist- 
ance varies, not only with the type and surface quality of the 
road, but also with the type, dimensions and quality of the tires 
on the wheels. The same tires were used in the experiments by 
Kennelly and Schurig. The air resistance of a given vehicle at 
any given speed is the same for all classes of pavement. The 
impact resistance of a road depends not only on the type and 
character of the road surface and the sizes of its irregularities, 
but also on the type, dimensions and quality of the tires on the 
wheels, the weight of the truck and the quality of its springs. 

Increasing the gross weight of the vehicle by 12 per cent, 
through load, was found to have no effect on tractive resistance 
within the observed speed limits for smooth roads in good con- 
dition; but on rough roads, a distinct increase in tractive resist- 
ance with this extra weight was observed. 



RURAL PUBLIC ROADS OF UNITED STATES 
AT CLOSE OF 1915 



Circular 63, United States Department of Agriculture. Prepared by 
Division of Road Economics, Office of Public Roads and Rural 

Engineering. 



the 



STATE 



Alabama 

Arizona 

Arkansas 

California 

Colorado 

Connecticut 

Delaware 

Florida 

Georgia 

Idaho 

Illinois 

Indiana , 

Iowa 

Kansas 

Kentucky , 

Louisiana 

Maine 

Maryland 

Massachusetts. . 

Michigan , 

Minnesota , 

Mississippi 

Missouri 

Montana 

Nebraska 

Nevada 

New Hampshire. 

New Jersey 

New Mexico 

New York 

North Carolina. 
North Dakota. . , 

Ohio 

Oklahoma 

Oregon 

Pennsylvania 

Rhode Island 

South Carolina. . 
South Dakota. . . 

Tennessee 

Texas 

Utah 

Vermont 

Virginia 

Washington 

West Virginia. . . 

Wisconsin 

Wyoming 



Total. 



TOTAL 
RURAL 
ROADS 



miles 

55,446 
12,075 
50,743 
61,038 
39,691 
14,061 
3,674 
17,995 
84,770 
23,109 
94,141 
63,370 

106,847 

111,536 
57,916 
24,562 
25,528 
16,458 
18,681 
74,089 
93,500 
45,778 
96,124 
39,204 
80,338 
15,000 
14,020 
14,817 
11,873 
80,112 
50,758 
68,000 
86,453 

107,916 
36,819 
91,556 
2,121 
42,220 
96,306 
46,050 

128,960 
15,000 
15,082 
53,388 
42,428 
32,024 
75,702 
14,381 



2,451,660 



TOTAL 

SURFACED 

ROADS 



miles 

5,915 

350 

1,200 

13,000 

1,750 

3,200 

300 

3,500 

13,000 

950 

11,000 

27,000 

1,000 

1,250 

13,000 

2,250 

3,000 

2,950 

8,800 

8,600 

5,500 

2,500 

8,000 

775 

500 

75 

1,800 

4,600 

450 

17,500 

6,500 

1,100 

30,920 

300 

7,780 

9,883 

1,246 

3,500 

850 

8,625 

12,000 

1,053 

3,478 

4,760 

5,460 

1,200 

14,050 

500 



276,920 



OS 

D 



10 

2 

2 
21 

4 
22 

8.0 
19.4 
15.3 

4 
11 
42 

1 

1 
22 

9 
11.7 
17.9 
46.6 
11.6 

5.9 

5.5 

8.3 

2.0 

0.6 

0.5 
12.8 
31.0 

3.8 
21.8 
12.8 

1.6 
35.8 

0.3 
21.1 
10.8 
58.8 

8.3 

0.9 
18.7 

9.3 

7.0 
23.1 

8.9 
12.8 

3.7 
18.5 

3.5 



11.3 



CASH 

EXPENDITURES 

FOR ROADS 

IN 1915 



$4,283,207 
1,076,178 
2,803,000 

20,753,281 
2,193,000 
3,484,944 
397,500 
5,501,135 
3,700,000 
1,974,636 
9,263,995 

13,000,000 

13,606,299 
5,510,000 
3,122,430 
3,569,709 
3,293,902 
5,630,000 
6,557,279 

10,174,738 
8,292,000 
2,900,000 
8,369,189 
3,676,318 
3,520,000 
250,000 
2,363,414 
7,163,584 
584,919 

24,255,648 
5,510,000 
2,500,700 

12,975,688 
3,410,000 
6,182,000 

12,541,257 
594,119 
1,000,000 
1,450,000 
3,503,500 
9,500,000 
1,213,100 
1,475,145 
4,018,399 
6,670,702 
2,759,212 
9,960,980 
441,291 



$266,976,399 



TOTAL STATE 

FUNDS 

FOR ROADS TO 

JANUARY 1, 

1916 



$586,405 

1,039,388 

165,000 

16,571,091 

1,024,751 

17,019,120 

224,695 

1,135 



572,812 
1,686,627 



255,935 

30,000 

616,715 

606,327 

5,865,209 

17,583,142 

18,999,992 

3,182,701 

4,288,174 

' 1,791, i72 

34,346 

377,850 

20,000 

3,259,789 

8,355,576 

662,955 

96,622,498 

38,500 



8,566,275 

30,323 

418,975 

30,801,211 

3,907,784 



3,500 



809,732 
3,671,564 
2,713,550 
8,552,789 

1130,978 

4,219,001 

43,237 



$265,350,824 



* Of this $118,000 was returned to the counties in 1911 by act of legislature. 

192 



REVENUES USED IN 1914 IN EACH STATE FOR 
PUBLIC ROAD AND BRIDGE PURPOSES AND 
TOTAL OUTSTANDING BONDS FOR ROADS 
AND BRIDGES AT CLOSE OF 1914 

From Bulletin 390, U. S. Department of Agriculture, Prepared by the Office 
of Public Roads and its State Collaborators 



STATE 



Alabama 

Arizona 

Arkansas 

California 

Colorado 

Connecticut 

Delaware 

Florida 

Georgia 

Idaho 

Illinois 

Indiana 

Iowa 

Kansas 

Kentucky 

Louisiana 

Maine 

Maryland 

Massachusetts. . 

Michigan 

Minnesota 

Mississippi 

Missouri 

Montana 

Nebraska 

Nevada 

New Hampshire. 

New Jersey 

New Mexico 

New York 

North Carolina.. 
North Dakota... 

Ohio 

Oklahoma 

Oregon 

Pennsylvania. . . 
Rhode Island. . . 
South Carolina.. 
South Dakota.. . 

Tennessee 

Texas 

Utah 

Vermont 

Virginia 

Washington 

West Virginia. . . 

Wisconsin 

Wyoming 



Total or ave . 



PUBLIC ROAD AND BRIDGE REVENUES 



Total 



$3,949,019. 
982,721. 

1,522,696. 
19,171,984. 

1,937,546. 

3,640 962. 
511 62a. 

2,280,255. 

3,688,172. 

1,371,468. 

8,734,712. 
14,233,985. 
10,187,507. 

5,544,048. 

2,474,621. 

1,777,572. 

2,642,006. 

6,000,652. 

6,091,875. 

9,261,998. 

6,458,940. 

3,960,377. 

5,513,048. 

2,888,400. 

1,796,277. 
245,013. 

1,590,464. 

7,208,287. 

556,398. 

23,231,964. 

5,2:15,490. 

2,402,383. 
14,334^245. 

2,112,680. 

5,310,466. 

10,424,580. 

446,496. 

1,024,480. 

1,217,809. 

2,370,560. 

9,920,079. 
803,070. 

1,023,941. 

3,224,528. 

7,944,717. 

2,483,747. 

9,880,240. 
669,661. 



00 
22 
20 
66 
23 
75 
00 
09 
25 
58 
77 
93 
32 
00 
00 
12 
79 
03 
30 
00 
07 
00 
71 
61 
69 
65 
11 
08 
82 
02; 
78 
52 
98 
80 
76 
00 
05 
37 
42 
16 
11 
63 
01 
82 
38 
00 
50 
16 



$240,263,784.46 



81 

30 
314 

48, 
258, 
139. 
126. 

45 

56. 

91. 
194. 

97. 

49. 

42. 

72. 
112. 
364. 
326. 
124 

69. 

86. 

57. 

73. 

22. 

20. 
113. 
486. 

46. 
292. 
102. 

34. 
165. 

19. 
144. 
113. 
205. 

24. 

12. 

51. 

76. 

91. 

71. 

60. 
187. 

77. 
130. 

44. 



22 

,38 
00 
09 
70 
90 
25 
71 
72 
22 
32 
06 
88 
92 
52 
37 
^ 
60 
08 
84 
06 
51 
40 
67 
37 
11 
44 
49 
86 
60 
75 
92 
99 
57 
23 
86 
76 
26 
64 
48 
92 
15 
86 
39 
25 
55 
50 
06 



;yJO 



$77.01 

8.63 

28.99 

123.17 

18.69 

755.50 

^0.37 

41.56 

62.80 

16.45 

155.85 

394.89 

183.27 

67.79 

61.58 

39.10 

88.37 

603.62 

758.00 

161.13 

79.88 

85.42 

80.22 

19.75 

23.38 

2.23 

176.11 

959.00 

4.54 

467.00 

107.00 

34.23 

351.84 

30.45 

55.54 

232.00 

418.50 

33.59 

15.84 

56.86 

37.80 

9.77 

112.22 

80.08 

118.87 

103.39 

178.81 

6.86 



.22 



$1,840 
4.810 
0.960 
8.060 
2.430 
3.260 
2.520 
3.020 
1.410 
4.210 
1.540 
5.270 
4.580 
3.280 
1.080 
1.073 
3.550 
4.630 
1.810 
3.290 
3.110 

2.W 
1.670 
7.680 
1.510 
2.900 
3.690 
2.830 
1.690 
2.540 
2.360 
4.160 
3.000 
1.274 
7.890 
1.360 
0.820 
0.670 
2.080 
1.080 
2.540 
2.150 
2.870 
1.560 
6.950 
2.030 
4.230 
4.590 



$80.79|$2.620 



-o o 



$0.6900 
0.7000 
0.3600 
0.6600 
0.4600 
0.3500 
0.5450 
1.0700 
0.4370 
0.8200 
0.3700 
0.7500 
1 . 1300 
0.2000 
0.2390 
0.3220 
0.6330 
0.4850 
0:i270 
0.4000 
0.4400 
0.9620 
0.3000 
0.8300 
0.3900 
0.2400 
0.3620 
0.2890 
0.7700 
0.2080 
0.6970 
0.6800 
0.2200 
0.1769 
0.5900 
0.2050 
0.0720 
0.3510 
0.3400 
0.3780 
0.3910 
0.4000 
0.4620 
0.3720 
0.7900 
0.2120 
0.4000 
0.3700 



$0.3500 



TOTAL STATE AND 
LOCAL BONDS 



$5,418, 

295, 

1,467, 

32,277, 

90, 

7 000 

1 280 

5 959 

127 

1,339, 

798, 

42,095, 

1,960, 



000.00 
000.00 
066.00 
000.00 
500.00 
000.00 
000.00 
199.00 
500.00 
000.09 
761.55 
357.34 
780.00 



705, 

1,588, 

785, 

12i,863, 

10,305, 

10,389, 

1,411, 

8,327, 

522, 

2,224, 



000.00 
835.00 
000.00 
700.00 
522.82 
029.43 
889.00 
172.00 
500.00 
050.72 



38,000.00 

675,000.00 

14,011,337.00 

157,000.00 

76,822,088.00 

8,955,300.00 



31,175,968.53 
1,440,000.00 
1,615,000.00 

127,547,659.00 

1,800,000.00 

460,000.00 



6,898,277.00 

14,615,017.00 

541,500.00 



5,650,994.93 

1,555,000.00 

1,303,000.00 

281,078.00 



$344,763,082.32 



193 



EXTENT OF SURFACED ROADS IN THE UNITED 
STATES AT THE CLOSE OF 1914 

From Bulletin 390, U. S. Department of Agriculture, Prepared by the Office of 
Public Roads and its State Collaborators 



Alabama 

Arizona 

Arkansas 

California 

Colorado 

Connecticut 

Delaware 

Florida 

Georgia 

Idaho 

Illinois 

Indiana 

Iowa 

Kansas 

Kentucky 

Louisiana.. . . . . 

Maine 

Maryland 

Massachusetts. , 

Michigan 

Minnesota 

Mississippi 

Missouri 

Montana 

Nebraska 

Nevada 

New Hamp- 
shire 

New Jersey 

New Mexico. .. . 

New York 

North Carolina. 
North Dakota. . 

Ohio 

Oklahoma 

Oregon 

Pennsylvania... 
Rhode Island... 
South Carolina. 
South Dakota. . 

Tennessee 

Texas 

Utah 

Vermont 

Virginia 

Washington 

West Virginia. . . 

Wisconsin 

Wyoming 



Total. 



Percent. 



MACADAM 



miles 

431.00 

11.23 

362.50 

837.40 

3.00 

923.42 

161.50 

829.16 

234.00 

42.50 

1,675.11 

10,291.29 

171.30 

194.30 

10,628.00 



55.36 

488.70 

834.30 

1,021.19 

120.25 

86.00 

1,531.05 

78.00 

39.21 

2.00 

61.87 
1,809.24 



5,717.97 
1,111.00 



12,903.87 

6.70 

1,000.72 

♦1,881.80 

352.92 

27.50 



4,550.50 

511.00 

49.00 

1.94 

1,177.89 

502.82 

771.92 

1,408.00 



64,898.43 



25.22 



BITUMI- 
NOUS 
MACADAM 



miles 

31.00 

13.50 

4.00 

877.90 



128.28 
35.50 
42.80 
87.00 
12.00 
121.53 
168.35 



59.03 



43.93 
1,042.31 
1,337.33 
94.50 
19.00 
29.50 
59.00 



1.30 



154.26 

417.63 

5.00 

3,168.63 

9.00 



1,066.29 

3.00 

137.25 

* 198. 33 

107.40 

3.50 

10.00 

148.00 

181.00 

15.50 



255.77 

165.52 

62.95 

183.00 



10,499.79 



4.08 



miles 

2,589.50 

125.70 

535.00 
3,563.59 

574.25 

1,057.93 

21.00 

42.50 

1,073.00 

168.00 

7,052.30 

20,264.59 

413.00 

151.85 
1,713.50 

430.00 
1,139.36 

243.95 
6,289.57 
5,230.25 
2,825.25 
1,281.10 
3,671.50 

514.25 
21.00 

193.00 

1,013.70 

2,858.52 

184.00 

5,802.97 

529.00 

955.00 

15,385.93 

6.90 

3,060.15 

*235.19 

230.10 

85.00 

212.00 

2,788.00 

5,258.98 

685.75 

1,165.42 

822.09 

3,924,48 

20.50 

9,597.00 

52.50 



45.11 



SAND 
CLAY 



miles 

1,916.00 
45.00 
175.00 
582.25 
450.12 
840.27 



1,163.00 

10,778.00 

449.00 

2.467.95 

150.25 

23.00 

758.60 



1,448.00 

2.26 

69.00 



1,375.27 

985.33 

604.25 

1,442.25 

14.00 

1,131.10 

67.00 

270.90 

561.40 

72.50 



4,313.50 



211.00 
105.00 
300.00 



3,101.00 
129.00 
613.00 

3,490.48 
401.00 



1,511.65 
83.50 



2,054.00 



116,058.12 44,154.73 



17.16 



miles 



1.33 



256.24 
1.72 



82.92 
34.75 



4.10 
.25 



.05 



.50 

i.oo 

'2;46 



148.53 



640.41 
*269".33 



.50 



26.35 

121.10 

2.40 



1,593.88 



0.62 



CON- 
CRETE 



m,iles 
1.00 



21.00 

929.19 

2.25 

24.22 



12.00 

.40 

4.50 

148.80 

53.17 

5.77 

1.35 

2.50 



10.51 
189.34 



107.30 
17.50 
14.00 

2.77 



7.53 



7.07 



244.19 
1.25 



315.67 
"28. '41 



2.00 

11.25 

2.50 



79.42 
18.50 
83.07 



2,348.43 



0.91 



MISCEL- 
LANEOUS 



mi7es 

20.00 
58.00 



3,489.40 
164.25 



25.50 

484.77 

168.00 

3.00 

57.70 



1.50 
38.75 



189 62 

1,510.89 

455.96 

44.69 



118.50 
5.00 
3.00 
2.00 



151.83 
250.67 



553.61 
40.00 



46.00 



199.87 

7,398.23 

3.00 

53.50 

12.00 



1,074.08 



274.67 
142.17 
140.00 
70.00 
72.00 
416.00 



17,738.16 



6.90 



TOTAL 

Surfaced 



miles 

4,988.50 

253.43 

1,097.50 

10,279.73 

1,193.87 

2,975.45 

243.50 

2,830.47 

12,342.12 

679.00 

11,606.31 

30,962.40 

614.57 

1,148.85 

12,403.28 

2,067 62 

2,762.36 

2,489.26 

8,505.89 

7,828.51 

3,967.83 

2,133.35 

6,712.57 

609.25 

1,304.54 

262.00 

1,659.63 
5,897.46 

261.50 

15,635.90 

6,003.75 

955.00 
30,569.17 

121.60 
4,726.40 

982.88 

693.42 
3,270.50 

363.00 
8,102.00 
10,526.79 
1,253.75 
1,442.03 
3,909.57 
4,922.09 
1,064.97 
13,399.47 

468.50 



257,291.54 



100.00 



• State roads only. 



194 



MOTOR-CAR REGISTRATIONS AND GROSS 
MOTOR- VEHICLE REVENUES, 1913-1915 

Circular 59, United States Department of Agriculture. Prepared by the 
Division of Road Economics, Office of Public Roads and Rural 

Engineering 



Alabama 

Arizona 

Arkansas 

California 

Colorado 

Connecticut 

Delaware 

District of Col- 
umbia 

Florida 

Georgia 

Idaho 

Illinois 

Indiana 

Iowa 

Kansas 

Kentucky 

Louisiana 

Maine 

Maryland 

Massachusetts. . 

Michigan 

Minnesota 

Mississippi 

Missouri 

Montana 

Nebraska 

Nevada 

New Haimpshire 

New Jersey 

New Mexico. . . . 

New York 

North Carolina. 
North Dakota. . , 

Ohio 

Oklahoma 

Oregon 

Pennsylvania. . . 
Rhode Island. . . 
South Carolina^ 
South Dakota.., 



MOTOR-CAR REQISTRATIONSl 


TOT A. 


1913 


1914 


1915 


1913 


25,300 

3,613 

3,583 

2100,000 

13,000 


8,672 

5,040 

5,642 

123,504 

17,756 


11,634 

7,753 

8,021 

163,797 

28,894 


$83,000 
27,545 
17,411 
75,000 
60,833 


23,200 
2,440 


27,786 
3,050 


41,121 
5,052 


316,667 
24,735 


4,000 

*3,000 

220,000 


4,833 
*3,368 
20,915 


8,009 

210,850 

25,000 


13,228 
^6,000 
12,000 


2,113 
94,656 
45,000 


3,346 

131,140 

66,500 


7,071 

180,832 

96,915 


35,160 
507,629 
150,345 


70,299 
34,550 


106,087 
49,374 


145,109 
72,520 


787,411 
186,066 


7,210 

210,000 

11,022 

14,217 

62,660 


11,766 
212,000 
15,700 
20,213 
77,246 


19,500 
11,380 
21,545 
31,047 
102,633 


52,000 
210,000 
138,509 
150,000 
764,154 


54,366 
46,000 
23,850 
38,140 
5,916 


76,389 
67,862 
5,694 
54,468 
10,200 


114,845 

93,269 

9,669 

76,462 

14,540 


190,329 
40,000 


173,510 
12,000 


13,411 
1,091 
8,237 

51,360 
1,898 


16,385 
1,487 
9,571 

62,961 
3,090 


59,000 

2,009 

13,449 

81,848 
5,100 


26,000 

3,323 

152,834 

661,446 

15,084 


134,495 
10,000 
15,187 
86,156 
23,000 


168,223 
14,677 
17,347 

122,504 
13,500 


255,242 
21,000 
24,908 

181,332 
25,032 


1,275,727 

60,000 

41,961 

457,538 

3,000 


13,975 
80,178 
10,295 
10,000 
14,457 


16,447 
112,854 
12,331 
14,000 
20,929 


23,585 
160,137 
16,362 
15,000 
28,724 


56,873 

841,062 

129,851 

10,000 

89,170 



TOTAL GROSS REVENUES 



1914 



$113,202 
34,077 
56,420 

1,338,785 
80,047 

406,623 
35,672 

20,147 

*6,736 

104,575 

58,580 
699,725 
432,309 

1,040,136 
268,471 

85,883 
212,000 
192,542 
268,231 
923,961 

(') 
132,398 

51,146 
235,873 

27,000 

34,325 
4,331 

185,288 

814,536 

19,663 

1,529,852 

89,580 

55,964 

685,457 

13,500 

77,592 

1,185,039 

157,020 

14,000 
125,000 



1915 



$180,744 
45,579 
80,551 

2,027,432 
120,801 

536,970 
55,596 

29,396 
260,000 
125,000 

121,259 
924,906 
587,318 

1,533,054 

387,588 

117,117 

75,600 

268,412 

386,565 

1,235,724 

373,833 
2160,540 

76,700 
323,289 

33,120 

2183,000 

7,875 

257,776 

1,062,923 

29,625 

1,991,181 

123,000 

79,245 

984,622 

154,892 

108,881 

1,665,276 

206,440 

15,000 

2180,000 



195 



Motor-Car Registrations — Continued 





MOTOR-CAR registrations! 


TOTAL QHOSS RKVBNUBB 




1913 


1914 


1915 


1913 


1914 


1915 


Tennessee 

Texas^ 


no,ooo 

32,000 
4,000 
5,913 
9,022 

24,178 
5,144 

34,346 
1,584 


»19,769 

40,000 

2,253 

8,475 

13,984 

30,253 

6,159 

53,161 

2,428 


87,618 

740,000 

9,177 

11,499 

21,357 

38,823 

13,279 

79,741 

3,976 


29,000 
16,000 

3,000 

111,460 

83,611 

48,356 

40,000 

190,770 

7,920 


39,538 

20,000 

4,852 

154,267 

120,814 

60,506 

60,648 

293,580 

12,140 


334,000 
20,000 


Utah 


^60,000 


Vermont 

Virginia 

Washington 

West Virginia. . . 

Wisconsin 

Wyoming 


218,480 
176,875 

238,717 

128,952 

431,977 

19,880 


Total 


1,258,062 


1,711,339 


2,445,664 


8,192,253 


12,381,951 


18,245,711 







^ Does not include motor cycles nor dealers' and manufacturers' licenses. 
2 Estimated. 

2 Registration law declared unconstitutional. 
* State registrations only. 
^ Total cars registered under perennial system. 
8 Registrations 1915 only. 

7 American Highway Association received report that there were 138,866 
automobiles licensed on April 1, 1916. 

PRODUCTION OF VITRIFIED PAVING BRICK 
IN THE UNITED STATES 



{From 


^^ Mineral Resources of the United States, 1915^') 








AVERAGE PRICE PER 


TBAB 


QUANTITT 


VALUE 


THOUSAND 




thousands 






1895 


381,591 


$3,130,472 


$8.20 


1896 


320,407 


2,794,585 


8.72 


1897 


435,851 


3,582,037 


8.22 


1898 


474,419 


4,016,822 


8.47 


1899 


580,751 


4,750,424 


8.18 


1900 


546,679 


4,764,124 


8.71 


1901 


605,077 


5,484,134 


9.06 


1902 


617,192 


5,744,530 


9.31 


1903 


654,499 


6,453,849 


9.86 


1904 


735,489 


7,557,425 


10.28 


1905 


665,879 


6,703,710 


10.07 


1906 


751,974 


7,857,768 


10.45 


1907 


876,245 


9,654,282 


11.02 


1908 


978,122 


10,657,475 


10.90 


1909 


1,023,654 


11,269,586 


11.01 


1910 


968,000 


11,004,666 


11.37 


1911 


948,758 


11,115,742 


11.72 


1912 


911,869 


10,921,575 


11.98 


1913 


958,680 


12,138,221 


12.66 


1914 


931,324 


12,500,866 


13.42 


1915 


953,335 


12,230,899 


12.83 



196 



OUTPUT OF VITRIFIED BRICK IN 1914 AND 

1915 BY STATES 

{From ^^ Mineral Resources of the United States, 1915") 





1914 


1915 




Quantity 


Value 


Aver- 
ago 
price 
per 
thou- 
sand 


Quantity 


Value 


Aver- 
age 
price 
per 
thou- 
sand 


Alabama 

Arkansas 

California 

Colorado 

Connecticut 
and Rhode 
Island 

Florida 

Georgia 

Illinois 

Indiana 

Iowa 


thousands 

18,679 

* 

1,800 

* 

* 
* 

16,470 

157,176 

42,937 

14,997 

50,707 

* 

7,733 

* 

26,217 

* 

* 
* 
* 

31,240 

293,381 

9,912 

151,200 

* 

1,684 

* 

* 

67,750 
39,441 


$248,525 
* 

39,705 

* 

* 
* 

234,855 

2,086,344 

576,892 

211,905 

594,229 

* 

120,562 

+ 

424,170 

* 

* 
* 
* 

515,672 

3,682,230 

127,792 

2,052,676 

* 

23,599 

* 

* 

899,215 
662,495 


$13.31 
12.14 
22.06 
11.52 

16.03 
12.00 
14.26 
13.27 
13.44 
14.13 
11.72 
12.74 
15.59 
16.12 
16.18 
22.50 
11.14 
15.00 
10.40 
16.51 
12.55 
12.89 
13.58 
15.26 
14.01 
10.00 
18.99 
13.27 
16.80 


thousands 

29,018 

* 

3,182 

* 

* 

17,193 

142,689 

35,237 

20,573 

47,511 

* 

4,420 

* 

* 
* 

561 

* 

24,154 

333,288 

16,537 

124,354 

* 

* 

14,861 
69,474 
59,844 


$374,387 
* 

66,784 

* 

* 

166,086 

1,796,350 

466,873 

300,785 

608,599 

* 

62,238 

* 

* 
* 

8,323 

* 

384,458 

4,017,758 

198,387 

1,638,518 

* 

* 

265,691 
841,067 
853,107 


$12.90 
12.00 
20.99 
11.59 

12.66 

9.66 
12.59 
13.25 
14.62 


Kansas 

Kentucky 

Michigan 

Minnesota 

Missouri 

Montana 

Nebraska 

New Jersey. . . . 
New Mexico... . 

New York 

Ohio 

Oklahoma 

Pennsylvania. . 

Tennessee 

Texas 


12.81 
10.85 
14.08 
14.18 
14.62 
22.01 
14.84 

12.00 
15.92 
12.05 
12.00 
13.18 
14.47 
15.45 


Virginia 

Washington.. . . 
West Virginia. . 
Other Statesf .. 


17.88 
12.11 
14.26 


Total 


931,324 


$12,500,866 


$13.42 


953.335t 


$12,230,8991 


$12.83 



* Included in ''Other States." 

t Includes all products made by less than three producers in one State. 

t In the total quantity and total value of vitrified brick are included, 
respectively, 824,359,000 vitrified brick sold for paving, valued at $11,114,- 
427, and 128,976,000 vitrified brick sold for other uses, valued at $1,116,472. 



107 



BROKEN STONE FOR ROAD BUILDING PRO 
DUCED IN THE UNITED STATES IN 
1914 AND 1915 

{From ''^ Stone in 1915/' G. F. Loughlin, "Mineral Resources of 

the United States" 



STATE OR TERRITORY 



Alabama 

Arizona 

Arkansas 

California 

Colorado 

Connecticut 

Delaware 

Florida 

Georgia 

Hawaii 

Idaho 

Illinois 

Indiana 

Iowa 

Kansas 

Kentucky 

Louisiana 

Maine 

Maryland 

Massachusetts . . 

Michigan 

Minnesota 

Missouri 

Montana 

Nebraska 

New Hampshire. 

New Jersey 

New Mexico 

New York 

North Carolina.. 

Ohio 

Oklahoma 

Oregon 

Pennsylvania. . . 
Rhode Island. . . 
South Carolina. 
South Dakota.. . 

Tennessee 

Texas 

Utah 

Vermont 

Virginia 

Washington 

West Virginia. . . 

Wisconsin 

Wyoming 



1914 



Quantity 



Short tons 

74,914 

2,600 

199,417 

1,707,230 

6,052 

360,443 

53,430 

159,524 

57,553 

41,832 



Value 



$75,528 
4,000 

140,442 

982,321 
10,100 

216,064 
33,501 
84,911 
37,088 
37,049 



1915 



Quantity 



Short tons 

49,972 



113,606 

1,567,505 

5,842 

728,014 

21,742 

102,517 

90,244 

34,413 



Value 



$42,116 



75,044 

902,462 

7,178 

330,174 

21,707 

56,381 

54,696 

36,366 



1,838,599 

2,089,103 

19,308 

27,248 

545,878 



893,889 

1,065,360 

17,438 

20,135 

323,075 



5,950 

404,523 

649,144 

530,823 

46,944 

466,143 

4,590 

32,137 

20,936 

827,705 



4,650 

349,833 

594,666 

267,702 

36,172 

363,302 

1,271 

27,300 

13,745 

674,202 



1,625,250 

1,792,261 

32,437 

20,046 

609,995 

830 

1,747 

334,153 

738,015 

510,524 

59,733 

553,049 

23,875 



2,267,264 

65,700 

3,453,360 

15,802 

218,379 

1,640,049 

61,373 

28,425 

14,120 

345,765 

196,051 

16,000 

17,978 

1,931,852 

162,777 

197,245 

1,000,667 



21,786,833 



1,408,490 

65,128 

1,748,075 

7,441 

157,267 

1,110,039 

72,255 

27,684 

11,300 

264,288 

119,218 

19,200 

13,563 

1,185,271 

87,259 

113,525 

635,618 



13,329,365 



14,845 

1,059,749 

547 

2,900,165 

69,238 

3,088,599 

46,430 

290,648 

1,844,626 

91,872 

27,111 

11,292 

441,298 

269,151 

6,500 

14,929 

2,193,898 

213,039 

196,068 

914,295 



22,710,070 



747,718 

910,462 

28,397 

15,591 

379,234 

664 

1,409 

274,644 

599,555 

224,734 

57,286 

383,022 

5,186 



12,416 

822,214 

407 

1,623,570 

73,404 

1,567,676 

29,764 

202,580 

1,218,446 

110,167 

26,566 

8,487 

369,296 

164,865 

3,750 

13,269 

1,538,149 

111,461 

129,106 

555,927 



13,735,546 



198 



GRAVEL AND PAVING SAND PRODUCED IN 
THE UNITED STATES IN 1914 AND 1915 

R. W. Stone in ^'Mineral Resources of the United States, 1915" 







PAVING SAND 






GRAVEL 




STATE 


1914 


1915 


1914 


1915 




Quantity 
(short 
tons) 


Value 


Quantity 
(short 
tons) 


Value 


Quantity 
(short 
tons) 


Value 


Quantity 
(short 
tons) 


Value 


Alabama 

Arizona.. 


5,849 


$4,538 


« 


* 


527,891 


$138,693 


547,656 

* 

831,668 

2,974,090 

* 

* 
16,518 

22,848 

« 

« 

4,424,527 
2,482,922 

1,554,199 

* 

448,897 

* 

854,180 

270.906 

2,457,094 

935,252 

991,119 

1,656,745 

7,422 

118,970 

17,491 

583,200 

2,112,557 

* 

2,828,887 

77,241 

« 

2,816,132 

« 

368,797 

1,814,902 

* 

* 

239,649 

540,653 

1,494.421 

251,216 

* 

519,850 
478,707 
114,273 

1,567,840 

* 

1,551,719 


$116,672 

• 


Arkansas 


106,578 


* 
26.714 






673.924 

3,258,718 

7,610 


278,876 

595,449 

3,310 


314.003 


California 

Colorado 


173,985 

* 


$42,841 

* 


709.602 

• 


Connecticut . . . 


* 

29,000 
5,610 


* 

7,000 
1,400 


* 


Florida 


* 
• 


* 
* 


98,435 
12,244 


10,637 
7,875 


4,495 


Georf^ia 


15,071 


Hawaii 


• 


Idaho 










* 

4,9.55.219 

4,184,093 

1,087,967 

160,283 

815,796 

738,510 

* 

760,204 

177,642 

2,140,359 

637,900 

1,500,291 

1,321,839 

13,310 

88,026 

« 

670.000 

2,204,880 

* 

2,149,310 

311,059 

10,875 

2,417,805 
505,737 
611,821 

1,766,651 

29,927 
196.909 
445,504 

1,183.646 
184.763 
822 
294,398 
4.57,137 
455,804 

1,294,893 
718,441 

142,215 


* 

793.422 
602,5.33 
205,820 
19,512 
208,770 

190,717 

* 

268,338 

50,795 

5.30,338 

236,704 

354,855 

257,827 

11,970 

16,435 

112,500 

672,433 

* 

891,762 
42,438 
5,725 
654,833 
225,559 
137,221 

387,845 

• 

4,995 

25,603 
183,296 
433,399 

45,162 
390 

87.379 
162,183 
125,618 
343,230 

48,245 

26,205 


• 


Illinois 


121.812 
158,443 
201,900 
137,582 

21,653 

* 


39,851 
55,290 
64,340 
37,206 

14,272 

* 


291,436 
240,053 
293,948 

244,103 

* 


73.645 
60,894 
97,008 

70,311 

* 


885,-548 


Indiana 

Iowa 


591,592 
313,327 


Kansas 


* 


Kentucky 


162,524 

« 


Maine 




* 


Maryland 

Massachusetts.. 

Michisran 

Minnesota 

Mississippi 


327,750 
78,3S0 

320,322 
36.458 


76,212 
33,161 

74,836 
15,666 


163,364 
47,239 

131,466 

* 

* 
* 

* 


71,517 
25,444 
14,021 

* 
* 

* 
* 


284,410 
169,772 
671,970 
175,084 
153,627 


Missouri 

Montana 

Nebrai^ka 

Nevada 


30,327 

* 

5,259 


6,485 

* 

610 


226,716 

5,500 

27.389 

1,775 


New Hamp- 
shire 










77,760 


New Jersey 

New Mexico. . . . 


110,260 


39,902 


160,256 

* 

51,363 


53,599 

• 

21,240 


447,388 

• 


New York 

North Carolina 


82,725 


34,148 


989.801 
23,652 


North Dakota. 










* 


Ohio 


407,025 


134,370 


501,359 


194,026 


922,379 


Oklahoma 


« 


Oregon 


3,368 
625,171 


2,607 
235,326 


i5,2i8 
291,599 


14,174 
106,828 


118.960 


Pennsylvania... 
Rhode Island... 


433,223 

• 


South Carolina. 










• 


South Dakota.. 

Tennessee 

Texai* 


* 

6,489 
46,460 
44,445 


* 

2.484 
14,315 
11,300 


* 

13,815 

11,904 

* 


* 
3,552 

2,950 

* 


36,826 
203.867 
393,121 


Utah 


29,772 


Vermont 


• 


Virginia 

Washington 

West Virginia... 

Wisconsin 

Wyoming 


• 

363,745 

44,617 

.. 222.298 


• 

86,796 
17,819 
71,560 


* 

83,827 

69,598 

206,094 


* 

27,628 
27,230 
67,340 


126,801 

129,016 

43.016 

349,941 

• 


Concealed 
totals 


36,645 


13.761 


391,150 


97,138 


443.791 




3,580,171 


1.121,999 


3,381,717 


1,077,346 


39,212,858 


9,398,897 


37,972,548 


9.598,391 



• Included in "Concealed totals. 



199 



THE REASONS FOR IMPROVING ROADS 

Good roads are desirable for three distinct reasons, which may- 
be called social, business and pleasure reasons. 

Social Benefits from Good Roads. — The social reasons for road 
improvements appeal to persons living in the country. The 
women who dwell in the country districts know better than any 
others what bad roads mean to themselves and their sisters on 
other fatms, and how utterly drab and hopeless is life in the coun- 
try with inadequate means of communication between themselves 
and almost their next-door neighbors. The country parson can 
tell what a handicap bad roads are in his work. Preaching two 
sermons on Sunday is but a part of his labors. He must visit 
his parishioners if he is to be the guide, counselor and friend he 
aspires to be. He knows by hard experience the difficulty of 
riding or walking over muddy roads and through oceans of slush 
to those longing for his comforting presence in time of sickness 
and death, and how hard it is to convey to those who are ill the 
things necessary for their recovery. The country doctor can 
likewise bear witness to the restraint and even suffering caused 
by bad roads. Taking men as they are in the large, the wonder 
is that there are any who would choose his profession, the most 
devoted and consecrated of all that serve humanity. He comes 
when he is called and where. His charity is unmeasurable, his 
rewards are insignificant. Time with him and with the patient 
waiting his aid is often the deciding factor between life and death; 
he knows full well the death rate due to isolation by poor 
highways. 

We cannot state in percentages the increase in the satisfaction 
of people with country life which follows the certainty a doctor 
can be obtained when he is needed. It is not yet possible to 
state in numerals how much better a man is for attending church 
regularly or how much better a farmer's wife is for driving over a 
good road whenever she wishes to call on her neighbors. But 
there is one thing to which everybody will agree; the schools of 
our rural territory are one of the great defenses of our national 
prosperity, and the education of our children is one of our best 
safeguards for the wise government of our republic. And so 
everyone will admit the importance of these figures: In eight 
typical rural counties studied by the U. S. Office of Public Roads 
during a period of five years, the average school attendance in- 
creased from 66 out of every 100 pupils enrolled before the roads 
were improved, to 76 out of every 100 after the improvements. 

200 



REASONS FOR IMPROVING ROADS 



201 



Ten per cent more children were helped, therefore, to become 
better citizens by an increase in taxation for roads amounting to 
only 9 per cent of the total tax for all purposes. 

Business Benefits from Good Roads. — The business advantages 
of road improvements to the owner of a farm can be stated even 
more definitely, for they can be measured in dollars and cents. 
In the investigation by the U. S. Office of Public Roads, just 
mentioned, the observations were carried out in New York, 
Virginia, Alabama, Florida and Mississippi, in districts which 
represent typical dairying, farming, mining and lumbering con- 
ditions, before and after the construction of roads. The amount 
of road improvements done in each of them, which produced the 
improved conditions which will be stated, were as follows: 



COUNTY 



Franklin, N. Y... 
Spotsylvania, Va 
Dinwiddie, Va. . . 

Lee, Va 

Wise, Va 

Dallas, Ala 

Manatee, Fla. . . . 
Lauderdale, Miss 




The investigations by the government's experts were not hasty 
observations from a buggy or automobile; they were painstaking 
searches through real-estate transfers, public records, railway 
reports, school reports and like sources of information, studied on 
the spot until their accuracy was fully established. They were 
made from year to year, moreover, to make sure that the local 
conditions were fully understood and the annual effect of a road 
improvement was ascertained beyond question. 

Real estate transfers showed that the percentage of increase 
in the value of rural property along these improved roads in about 
five years was as follows: Franklin, 9 to 114; Spotsylvania, 63 to 
80; Dinwiddie, 68 to 194; Lee, 70 to 80; Wise, 25 to 100; Dallas, 
50 to 100; Manatee, 50 to 100; Lauderdale, 25 to 50. The 
transfers on which these figures are based are mostly for prop- 
erty within a mile of the improved roads. 

In each county the extent of the districts sending vehicles to 
the improved road was carefully determined in much the same way 
that the drainage area of a stream is ascertained. The products 
of these districts and the proportion of them hauled over the 
roads were then ascertained. The railway shipments from and 



202 AMERICAN HIGHWAY ASSOCIATION 

into the districts were investigated. In case of doubt the actual 
travel on the roads was ascertained by counts of the vehicles and 
their loads. The average length of the haul on the roads was 
found out. From all these statistics, given in detail in the report, 
it is shown that the cost of hauling one ton one mile on the roads 
of these counties was decreased from an average of 33.5 cents 
before highway improvements were made to 15.7 cents after- 
ward. This saving of 17.8 cents per ton per mile amounts to 
$627,409 in all. To accomplish it the additional taxes amounted 
to only 6.3 cents per ton per mile, leaving a net saving of 11.6 
cents per ton per mile. 

Roads as Sources of Enjoyment. — It is unfair to object to includ- 
ing the pleasure obtained by riding comfortably through the 
country as one of the returns we receive from our road taxes. 
It is just as proper to include that kind of pleasure as a justifiable 
object of expenditure as the investments for liquors, tobacco, the 
theatre and confectionery. E. W. James, one of the road experts 
of the United States government, recently made the following 
statement on the subject: 

The people of the United States spent in 1915 $2,500,000,000 for spiritu- 
ous and malt liquors $800,000,000 for tobacco, $450 000,000 for the "mov- 
ies," $300,000,000 for candy, $200,000,000 for soda water and $50,000,000 
for chewing gum. The total for these pleasures is $4,300,000,000. So I 
think it conservative to say that the average man is willing to pay some- 
thing for pleasure. There can be no question about the pleasure derived 
from riding on good roads, and that a part of the money invested in such 
roads can be logically justified on the score of this pleasure. After all, 
the total annual expenditures on roads in the United States is only equal 
to our purchase of candy and merely one-eighth of the money spent on 
liquor. 

The Townsman's Interest in City Roads. — When the average 
townsman dresses in the morning, a large part of the clothes he 
puts on are made of cotton, which has to be teamed over a good 
many miles from the plantations to the shipping points. If he 
has fruit, cereal, eggs and toast for breakfast, let us say, about 
everjrthing he eats has been hauled over several miles of roads, 
either to be shipped to him or to the mills where it is prepared for 
shipment. A large part of the furniture in his home and at his 
office has been made from hardwood hauled over the roads. 
These and other things which anybody can list for himself must 
all vary in price to the townsman with the cost of haufing them 
from the farms and forests to the mills or railroad stations. Just 
what this fact means has been stated by J. E. Pennybacker, the 
highway economist of the United States Office of Pubhc Roads, 
as follows: 



REASONS FOR IMPROVING ROADS 203 

The public roads throughout the country, which constitute the primary 
means of transportation for all agricultural products, for many millions 
of tons of forest, mine and manufactured products, and \vhi(;h for a large 
percentage of farmers are the onlj^ avenues of transportation leading from 
the point of production to the point of consumption or rail shipment, 
have been improved to only a slight extent. By reason of this fact, the 
prevailing cost of hauling over these roads is about 23 cents per ton pep 
mile. More than 350,000,000 tons are hauled over these roads each year, 
and the average haul is about 8 miles, from which it can readily be seen 
that our annual bill for hauling over the public roads is nearly #650,000,000. 
The cost per ton-mile for hauling on hard surfaced roads should not exceed 
13 cents. It is therefore evident that if our roads were adequately im- 
proved a large annual saving in the cost of hauling would result. 



The difference between 23 and 13 cents is 10 cents, which is 
the ton-mile tax of poor roads which the city people pay, for most 
of the hauhng is toward markets or shipping points and the cost 
of this hauhng is part of the total expense of products of the land 
to the consumer. The total is about $280,000,000, which the 
45,000,000 people Uving in the cities and towns of the United 
States pay annually on account of poor roads. This averages 
over $6 a year per person. 

Poor roads put a much more serious drain on the townsman's 
pocket-book, however. His food is costing him more every year, 
and he therefore has a very close, personal interest in having the 
agricultural lands farmed in such a way that they yield their 
largest returns at the lowest working cost. This means more 
than producing milk and vegetables at a low cost; it also includes 
raising at low expense the wheat and corn from which his flour 
and meal are made, producing fowls and hogs economically, and 
reducing the cost of growing cotton. How many inteUigent 
young men, able to earn a good Hving in a city, will live in the 
country if they have to travel through miles of mud or dust, at 
decided physical discomfort, in order to market their products, 
meet their friends or buy their supplies? How many young 
women will be willing to live in the country where bad roads 
isolate them, with only the sparrows for companions, with the 
doctor almost inaccessible, the schools difficult for the children 
to reach, and church-going a real labor? Yet if the townsman is 
to have the things he eats grown for him efficiently and economi- 
cally he must take his part in making country life agreeable and 
profitable to these intelhgent young people. It means a saving 
of dollars and cents to him. 

Our American Roads. — The length of the rural roads in the 
United States at the close of 1915 is given in the table on page 
192. This table shows that only 11.3 per cent of the total mile- 
age at that time had been surfaced, and that only 2 per cent had 



204 AMERICAN HIGHWAY ASSOCIATION 

been built by the state highway departments or with more or less 
financial or engineering assista/nce from the states. 

It has been estimated that about 80 per cent of the total travel 
on these roads is done on about 15 per cent of their total length. 
The percentages vary in different states. The Iowa Highway 
Commission found that from 10 to 15 per cent of the roads of each 
county are main traveled routes, which it is proper to construct 
and maintain, under the Iowa highway laws, at the expense of 
the county as a unit. The remaining roads are of less general 
use and are constructed apd maintained by the townships through 
which they pass. 

This division of our highways into main routes and local roads 
is of fundamental importance in road administration. Public 
money must be used so as to yield the greatest good to the great- 
est number of people. But it is human nature for a man living 
a mile or more from a main road to complain that he is unfairly 
treated if he must travel over a dirt road part of the way to town 
while a neighbor has a good, hard-surfaced road running by his 
place. As a matter of fact, although the hard road does not 
reach his farm it does help him materially, as Prof. B. K. Cogh- 
lan, of the Texas Agricultural and Mechanical College has 
shown by a recent investigation. He reports: 

Where a farmer lives at a considerable distance from the improved 
road he will still derive some benefit. In one county, where the gravel 
roads extend only about 8 miles from town, the farmers living several 
miles beyond haul wood during the dry spells and pile it at the end of the 
gravel road; then when bad weather comes and it is impossible to work in 
the fields they haul this wood to town. In another case two teams are 
used until the improved road is reached, when one team is unhitched and 
left with a friend, and the man proceeds to town with the other. In a 
third instance, where it formerly took two days to haul a load to market, 
since a good road has been built for about one-half of the distance, two 
wagons, with two teams each, haul one day until the good road is reached 
when all the load is put on one wagon, which proceeds to town with one 
team, the other three teams returning home. 

Our main roads which carry four-fifths of the traffic present 
problems which are often quite different from those of the local 
roads. Highways must be built to carry the traffic over them at 
the lowest possible cost for both construction and maintenance. 
Where the traffic is light, as on local roads and some main roads, 
comparatively inexpensive types of construction can be main- 
tained at small expense and are therefore better than more ex- 
pensive types because more miles of them can be provided for 
the same total cost than is the case with expensive types of con- 
struction. As a rule, however, we are trying to get too much 
work from inexpensive roads and at the same time we are neglect- 



REASONS FOR IMPROVING ROADS 205 

ing to maintain them in a condition for giving the most service. 
For many years to come, a large part of our roads will be earth, 
top-soil, sand-clay and gravel. That is no reason, however, for 
their being mud holes in wet weather or sources of blinding dust 
in dry weather. Well graded, drained and maintained roads of 
these types are pleasant to ride over and inexpensive to maintain, 
unless they are called upon to carry more travel than they are 
capable of supporting. Then they fail just as a beam fails when 
it is overloaded. The beam is all right for a given loading, but 
all wrong for a greater one. A road may be all right for a certain 
travel but all wrong for a greater travel; the failure to recognize 
this is responsible for a large part of the waste of road taxes 
today. 

Different Classes of Road Improvements. — The improvement of 
roads comprises a number of classes of work. People who speak 
of road improvements in Missouri probably refer to grading and 
draining, while road improvements in Massachusetts usually 
signify the construction of a hard surface on a road already 
graded and drained. Such use of the word ''improvements" 
indicates how varied are the really pressing highway needs of 
different parts of the country and the importance of studying the 
local resources and transportation requirements of a district be- 
fore planning the improvement of its roads. 

The first thing to be considered in planning good roads is the 
amount of money which it is wise for a community to spend for 
them. Most estimates of this nature are based on the existing 
annual tax receipts available for the purpose. This is not the best 
basis for a sound judgment. A family of three persons can make 
an income of $1800 go farther than a family of six persons can. It 
is the same with ro^ds. To find out roughly how much money 
can be devoted to road work it is best to divide the assessed valu- 
ation of the district by the miles of roads in it. This gives the 
valuation, or taxable wealth, of the district per mile of road. 
For instance. Lake County, Mich., has a valuation of only $5420 
per mile, showing that not even the entire wealth (>f the county 
is sufl[icient to improve all its roads. Wayne County, Mich., on 
the other hand, has a valuation of $514,931 per mile, indicating 
its financial ability to carry out any kind of road improvements 
in reason. In a rich agricultural district like Calhoun County, 
Mich., the valuation is $52,294 per mile, indicating that it is 
financially able to construct whatever kind of main roads may 
be best suited for the travel on them. We look with pity on the 
young saleswoman who spends all her money on clothes she does 
not need, and yet we complain when a county with a very low 
valuation per road-mile is not intersected with roads as smooth 



206 AMERICAN HIGHWAY ASSOCIATION 

as the top of a billiard table. This shows that we have our fool- 
ish ideas, like the flighty saleswoman. 

There is a measure of the need for roads, just as there is a 
measure of the financial resources for roadbuilding. This meas- 
ure is the travel the road is carrying now and the probable in- 
crease in the travel during the next five to ten years. The im- 
provement of a country road results in the slow development of 
property along it, so that there is a slow annual increase in 
what is called the residential travel. If the road is on a through 
route between important cities some distance apart, there may 
or may not be a material increase in the foreign travel, by which 
is meant the travel between these cities. This can only be de- 
termined by a study of local conditions. The residential travel 
can be actually counted, however, and this ought to be done. 
The state highway department or the United States Office of 
Public Roads and Rural Engineering at Washington will furnish 
instructions for the work, which can be done by school children 
under the direction of their teachers. This is a kind of child 
labor which no reformer will weep over and the efficiency expert 
will approve. 

The travel over a road wears it out in different ways, according 
to the number and character of the vehicles, the relative propor- 
tion of horse-drawn vehicles and automobiles, the climatic con- 
ditions and the construction of the road. For the same travel, 
a road adopted for a moist section with cold winters is needlessly 
expensive for a dry section with little frost. Some types of roads 
wear out quickly but are easily maintained, other types with- 
stand travel well but when they need repairs the work is expen- 
sive. All these things must be considered in determining the 
annual cost of a road, which is done in the following way. 

The first element of this cost is the first cost of construction per 
mile of road, including all engineering expenses. Knowing the 
travel over the road, an expert can estimate the number of years 
such a road will serve its purpose, if properly maintained, before 
reconstruction is necessary. This cost divided by the number of 
years of service gives the annual first cost. To this must be added 
the annual interest on the first cost per mile. If the construction 
costs are met by the proceeds of a bond issue, the interest and 
sinking fund charges on the bonds take the place of the annual 
first cost and interest just mentioned. The annual cost per mile 
of maintaining the road in serviceable condition is the last item 
to be estimated. The sum of all these items is the total annual 
cost per mile of the road, and this figure is the most important 
one to the taxpayers. But another unit for measuring cost, 
which is sometimes very useful, is the cost of the road per vehicle 
mile. This is obtained by dividing the total annual cost per 



REASONS FOR IMPROVING ROADS 207 

mile by the number of vehicles using the road annually. The 
type of construction which gives the lowest cost per vehicle mile 
is generally the best to employ. 

While the preceding notes explain the steps to be taken in 
planning a good road, they cannot supply the good judgment 
necessary to take the steps wisely. We admire the skill of a 
slack-rope gymnast but we are not foolish enough to emulate 
him. The skill and knowledge needed to select the right type of 
construction for a road are greater than those required by the 
slack-rope performer, and yet our minds are so warped by con- 
stant use of roads that we are strongly inclined to think we are 
able to do the work of road engineers. We will be losing money 
in our road planning until we stop this foolishness. 



INDEX 



Absorption of water by earth, 20 
Accidents, on roads, 25 
Aggregates for concrete, 93 
Alabama, road mileage, 192, 193, 194 
Andesite, 76, 87 

properties, 77 
Annuity bonds, 187 
Appalachian oil fields, 110 
Arid regions, roads, 46 
Arizona, funds for roads, 193 

motor cars, 195 

road mileage, 192, 194 
Arkansas, funds, 193, 195 

motor cars, 195 

road mileage, 192, 194 
Aspha-bric, 176 
Asphalt, see Bitumen 

Bermudez, 120 

blocks, 148 

California, 122 

Cuban, 122 

definitions, 117 

Maracaibo, 122 

Mexican, 122 

mixers, 145 

natural, 118 

oil, 118 

Trinidad, 118 
Asphaltenes, 116 
Augite, 321 

Automobile accidents, 25 
Automobile registration, 193 



Banking curves, 230 
Basalt, 75, 87 

properties, 76 
Base, see Foundation 
Belts for finishing concrete, 01 8 
Berm ditches, 22 
Bermudez asphalt, 120 
Binders, bituminous, 124 

clay, 51, 52, 53, 56, 58 

glutrin, 72 

gravel and screenings, 71, 72 

iron oxide, 51 

rock powder, 53 
Biotite, 83 
Bitumen, definition, 117 

ductility, 126 

fixed carbon, 116 

float test, 125 

fluxing solid, 123 

gilsonite, 122 

grahamite, 123 

hydrocarbons, 116 

inorganic matter, 116 

insoluble organic matter, 116, 121 

manjak, 123 

native solid, 117 

paraffin, 116 

penetration, 121 

solid, semi-solid and liquid, 117 

solubility in carbon disulphide, 114 

in carbon tetrachloride, 122 

in naphtha, 116 

viscosity, 125 
Bituminous fillers for joints, 173 



Bituminous roads, 138 

concrete, 144 

macadam, 139 
Blasting, 38 
Blowing oils, 114, 116 
Bonds, 180 
Box, 57, 60, 69 
Brick, paving, 157 

cubical, 176 

impregnated with asphalt, 176 

production, 196, 197 
Brick roads, 157 

on 1-inch concrete base, 178 
Bridges, 34 

avoided by relocation of roads, 2 

overflow, 36 

size of waterways, 254 
Byerly process of blowing oils, 114 

Calcite, 84 
Calcium chloride, 74 
California asphalt, 122 

banking curves, 9 

funds for roads, 193 

motor cars, 195 

oil, 110 

regulations regarding surveys and plans, 12 

road mileage, 192, 194 
Carbon disulphide test for bitumens, 114 
Catchbasins, 29 
Cement, standard specifications for Portland, 

107 
Cementing value of rock powders, 85 

test, 86 
Chert, 75, 88 
Chlorite, 84 
Clay, absorption and retentivity, 20 

for sand-clay roads, 47 

slope in cuts and fills, 5 
Clearing right-of-way, 39 
Colorado, funds for roads, 193 

motor cars, 195 

road mileage, 192, 194 
Concrete, cement, curing, 103 

expansion and contraction, 100 

finishing, 102 

mixing, 97, 101 

placing, 98 

proportions, 95 

quantities of sand, cement and stone re- 
quired for roads of different widths and 
thicknesses, 96, 97 
Concrete, bituminous, 144, 155 
Concrete roads, 90 

surfacing, 1.54 
Connecticut, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Contracts, plans for, 4 
Costs per mile corresponding to different 

costs per square yard, 70 
Cross-drains, 27, 91 
Cross-sections of roads, concrete, 92 

influence on drainage, 20 

Wisconsin standards, 6 
Crown of roads, 21, 92 
Crushing gravel, 54 

rock, 66 



209 



210 



INDEX 



Cuban asphalt, 122 * 

Culverts, 32 

avoided by relocation, 23 

driveway, 26 

headwalls, 33 

size, 29 
Curbs, 162 
Curves, 8, 9 
Cushion for brick, 165 
Cut-back bituminous products, 133 
Cuts, 38, 42 

Deferred serial bonds, 188 
Delaware, road mileage, 192, 194 

funds, 193 

motor cars, 195 
Deval test, 86 
Diabase, 75, 87 

properties, 77 
Diorite, 75, 87 

properties, 77 
Distillation test of tar, 137 
Distributors of oil, 142 
Ditches, 24 

accidents by ditching vehicles, 28 

berm ditches, 22, 24 

marsh-road, 21 

outlets, 22, 26 

recommendations of American Railway En- 
gineering Association, 23 

steep grades, 19, 25 

summits in, 25 

water brakes, 25 
Dolomite, 84, 87 

properties, 80 
Dragging, earth roads, 43 

embankments during construction, 40, 42 

gravel roads, 56, 57, 63 

road plane, 40 

sand-clay roads, 49 
Drainage, 19, 68, 91 

size of culverts, 30 
Driveway culverts, 26 
Dubbs process of refining petroleum, 113 
Ductility test of bitumens, 126 
Dumping boards, 70, 141 
Dun's culvert formula, 31 
Durax pavements, 176 

Earth roads, 32 

oiling, 146 
Embankments, 39, 42 

accidents on, 25 

building in layers, 39, 90 

drainage, 23, 24, 29 

in flat country, 22 

in marshes, 21 

protection against scouring, 26, 33 

slopes, 5 
Engineering, bridge, 35 

importance in road work, 3 

regulations of California commission re- 
garding surveys and plans, 12 
Epidote, 84 
Excavation, 38 
Expansion joints, 99, 174 

Feather-edge gravel and broken stone roads, 67 

Feldspar, 83 
Fillers for joints, 99 
Fills, see Embankments 
Finishing concrete surfaces, 102 
Flash point of oils, 114 
Float test of bitumens, 125 



Florida, funds for roads, 193 

motor cars, 195 

road mileage, 192, 194 
Fluxes, 116, 123 
Fords, 36 

Forms for concrete roads, 99 
Foundations, brick roads, 163 

bridges, 35 

concrete roads, 90 

culverts, 33 

gravel roads, 67, 60 

macadam roads, 68 

on sand, 55 

steep grades, 20 

telford, 27, 68 
French coefficient of wear, 86 
Funds for road work in the different States, 193 

Gabbro, 75, 87 

properties, 78 
Garnet, 83 
Georgia, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Gilsonite, 122 
Glutrin, 62, 72 
Gneiss, 75, 88 

properties, 82 
Grade crossings, 9 
Graders, 40 

elevating, 42 

gravel roads, 56, 58, 60 

sand-clay road uses, 49 
Grades, 1, 4, 11 

effect on traction, 4 

improved by relocation, 3 
Grading, 38, 40 

light cuts on hard roads, 6 
Grahamite, 123 
Granite, 75, 87 

properties, 79 
Gravel bed, 57 
Gravel, crushing, 54 

for concrete roads, 94 

length of road which a load of gravel of 
given size will cover to given loose depths, 
61 

mechanical analysis, 53 

production, 199 

quantity of loose gravel for a mile of road of 
different widths and thicknesses, 55 

quantity required to give different depths 
when lying loose on a mile of road of 
different widths, 55 

road-building grades, 61, 67 

screening, 54, 59 

spreading, 61 

weight, 56, 62 
Gravel roads, 51 
Gravel-asphalt roads, 147 
Grout joints for brick, 171 
Grubbing right-of-way, 39 
Guard rails, 25 
Gulf oil field, 110 



Hardness, test for, 85, 121 
Harrowing, bituminous macadam, 141 

broken stone roads, 71 

gravel roads, 56, 58 
Heating binders and road oils, 130, 142, 145 
Highway maintenance, see Maintenance of 

Roads 
Hillside brick, 159 
Hornblende, 83 
Hydrocarbons, 109, 116 



INDEX 



211 



Idaho, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Illinois, bituminous roads, 141, 142, 144, 145 

brick roads, 161, 167, 169, 178 

funds, 193 

gravel roads, 52, 57 

motor cars, 195 

oil field, 110 

road mileage, 192, 194 
Indiana, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Inorganic matter in bitumen, 116 
Iowa, automobile accidents, 25 

funds for roads, 193 

motor cars, 195 

road mileage, 192, 194 

Joints, brick roads, 169, 171 

concrete roads, 99 
Joint fillers, 99, 175 

Kansas, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Kaolin, 84 
Kentucky, funds, 193 

motor cars, 195 

organization for road dragging, 45 

road mileage, 192, 194 

Layers in embankments, 39 
Lima-Indiana oil fields, 110 
Limestone, 84, 87 

properties, 79 
Loam, absorption and retentivity, 20 

slopes in cuts and fills, 5 
Location of roads, 1 

at grade crossings, 10 
Loss by volatilization of oils, 114 
Louisiana, funds, 193 

motor cars, 195 

road mileage, 192, 194 

Macadam roads, bituminous, 139 

water-bound, 64 

surface treatment, 152 
Magnetite, 83 
Maine, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Maintenance, bad roads, 1 

bituminous roads, 153 

concrete roads, 104 

dragging, 43 

earth roads, 43 

gravel roads, 62 

macadam roads, 73 

sand-clay roads, 50 
Malthenes, 116 
Manjak, 123 
Maps, California commission regulations, 16 

Vermillion County improvements, 4 
Maracaibo asphalt, 122 
Marble, 75, 88 

properties, 81 
Marshes, roads across, 21 
Maryland, bituminous concrete, 145 

brick roads, 175 

funds, 193 

motor cars, 195 

road mileage, 192, 194 
Massachusetts, bituminous roads, 140, 144 

funds, 193 

gravel-asphalt roads, 147 



Massachusetts, motor ciirs, 195 

road mileage, 192, 194 
Mastic joint fillers, 174 
Mexican asphalt, 119, 122 
Mica, 83 
Michigan, funds, 193 

gravel for roads, 51 

motor cars, 195 
Michigan, road mileage, 192, 194 

water-bound macadam, 64 
Mid-continent oil fields, 110 
Mileage of roads, 192, 194 
Minerals in road building rocks, 83 
Minnesota, funds, 193 

motor cars, 195 

water-bound macadam, 64 

road mileage, 192, 194 
Mississippi, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Missouri, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Mixers for bituminous concrete, 341, 391, 400 
Mixers for concrete, 97, 101 
Mohs, scale of hardness, 83 
Monolithic brick roads, 167 
Montana, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Motor trucks, road widths needed for, 7 
Muscovite, 83 

Nebraska, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Nevada, funds, 193 

motor cars, 195 

road mileage, 192, 194 
New Hampshire, funds, 193 

gravel roads, 63 

motor cars, 195 

road mileage, 192, 194 
New Jersey, broken stone specifications, 68 

funds, 193 

gravel for roads, 51 

motor cars, 195 

road mileage, 192, 194 

telford specifications, 68 
New Mexico, funds, 193 

motor cars, 195 

road mileage, 192, 194 
New York, bituminous roads, 141, 146 

brick roads, 161 

funds, 193 

grade crossing regulations, 10 

motor cars, 195 

road mileage, 192, 194 

telford specifications, 68 

water-bound macadam, 64, 67, 153 
North Carolina, funds, 193 

motor cars, 195 

road mileage, 192, 194 
North Dakota, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Note-keeping on surveys, 12 
Nozzles for road oil, 142 

Ohio, bituminous macadam, 141 
brick roads, 161, 168, 173 
funds, 193 
macadam, 67 
motor cars, 195 
road mileage, 192, 194 



212 



INDEX 



Oiling roads, 150 

gallons of bituminous material per mile 
of road for different rates of application, 
140 

gravel, 63 

macadam, 74 
Oils, classification, 109 

equivalent volumes at different tempera- 
tures, 131 

classification, 109 

road, 124, 135 

shipping, 128 

specific gravity, weight and volume at 60°, 
129 
Oklahoma, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Oregon, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Orthoclase, 83 
Outlets, ditches, 22, 26 

drains, 29 

Paraffin, 109, 116 

Patrol system of maintenance, 297 
Penetration roads, 126, 139 
Penetration test of bitumens, 121 
Pennsylvania, bituminous roads, 141, 153 

brick roads, 161, 167, 175 

funds, 193 

motor cars, 195 

road mileage, 192, 194 
Petroleum, 109 

specific gravity, degrees Baum6, weight 
and volume at 60°, 112, 129 
Pipe culverts, 33 
Plagioclase, 83 
Plans, Vermilion county improvements, 4 

California commission regulations, 16 
Plowing, in grading, 38 

sub-grades, 60 
Ponding concrete roads, 96, 104 
Pouring cans, 143 
Pumping road oil, 128 
Pyro-bitumens, 118 

Quartz, 83 
Quartzite, 88 
properties, 81 

Rattler test, 160 

Refining petroleum. 111 

Residuums, 114 

Resistance of roads to traction, 189 

Retentivity of clay, loam, etc., 20 

Rhode Island, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Rhyolite, 75, 87 

properties, 78 
Rights-of-way, 7 

clearing and grubbing, 41 
Road machines (graders), 40 
Roadbed, elevation for drainage, 22; grading, 

38, 60 
Road plane, see Dragging 
Roads, asphalt block, 148 

bituminous, 138 

brick, 157 

concrete, 90 

costs per mile corresponding to different 
costs per square yard, 70 

dragging, 44 

drainage, 19 

earth, 37 



Roads, grade crossings, 9 

grades, 4 

gravel, 51 

gravel-asphalt, 147 

location, 1 

macadam, bituminous, 138 

water-bound, 64 

maintenance, 1, 43, 50, 62, 73, 104, 153 

mileage, 193, 195 

resistance to traction, 189 

sand-clay, 47 

sand-oil, 147 

sections, 6, 21 

semi-arid regions, 46 

top-soil, see Sand-clay 

widths, 6, 21, 92 
Rock crushing, 66 
Rock for roads, see Stone 
Rolling roads, earth, 43 

gravel, 58 

macadam, bituminous, 62, 63, 146 

sand-clay, 49 

water-bound, 71, 72 
Runoff, factors influencing, 30 

Sand, absorption and retentivity, 20 

for concrete, 93 

for cushion for brick, 166 

production of paving, 199 

slopes in cuts and fills, 5 

weight, 56 
Sand-asphalt roads, 147 
Sand-clay roads, 47 
Sandstone, 75, 87 

properties, 80 
Schist, 75, 84, 88 

properties, 82 
Scrapers for grading, 38 
Screening gravel, 59 

rock, 67 
Seal coats, 139, 144, 146 
Section-line roads, 2 
Serial bonds, 187 
Shale, 75, 88 
Shoulders, gravel roads, 58 

macadam roads, 72 

concrete roads, 92 

bituminous roads, 142 
Shrinkage of embankments, 40 
Silt, absorption and retentivity, 20 
Single-track roads, 7, 92 
Sinking fund bonds, 185 
Slag, 89 
Slaking clay, 47 

rock powder, 85 
Slate, 75, 88 
Slopes of cuts and fills, 5 

protection, 26, 33 
South Carolina, funds, 193 

motor cars, 195 

road mileage, 192, 194 
South Dakota, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Specific gravity determinations of oil, 114 
Steam shovels, 38, 
Stone, crushed, see Rock 

length of road which a load of stone of given 
size will cover to given loose depths , 61 

production, 198 

quantity required to give different depths 
when lying loose on a mile of roadway of 
different widths, 55 

sizes, 67 

weight, 66 
Stone, for bituminous roads, 138, 141, 144 



INDEX 



213 



Stone, for concrete roads, 93, 96 

for water-bound macadam, 64 

mineral composition, 75 

physical properties and tests, 85 
Straight-run bituminous products, 133 
Streak of minerals, 121 
Sub-grades, brick roads, 163 

concrete roads, 90 

gravel roads, 60 

macadam roads, 69 
Summits in ditches, 25 

on roads, 5 
Surfacing roads with bituminous materials, 

150 
Surveys, regulations of California commis- 
sion, 12 
Swamp roads, 21 

Talbot's culvert formula, 30 
Tar and tar products, 132 
Telford foundations, 27 
Tennessee, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Texas, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Tile drains, 27 

Top soil roads, see Sand-clay Roads 
Toughness, test for, 85 
Traction, effect of grades, 4 

resistance of roads to, 189 
Tractors, 41, 100 
Trap, 83, 84, 87 

Trench, for gravel and broken stone, 57, 60, 69 
Trinidad asphalt, 118 
Trumbull process of refining petroleum, 113 

Underdrains, 27 
for embankments, 23 
size, 24 



Underpasses on Now York highways, 10 
Utah, funds, 193 

motor cars, 195 

road mileage, 192, 194 

V-drains, 27 
Vermont, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Vertical curves, 5 
Virginia, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Viscosity of bitumens, 125 
Volatilization test of oils, 114 

Wagons, 38 

spreader, 70 
Washington, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Water-bound macadam roads, 64 
Water-brakes, 25 
Water for concrete, 101 
Wear of rocks, test, 86 
Weathering of rocks, 85 
Wentworth's culvert formula, 32 
West Virginia, funds, 193 

motor cars, 195 

road mileage, 192, 194 
Width of roads, 5, 92 

at grade crossings, 10 
Wisconsin, funds, 193 

gravel roads, 59 

motor cars, 195 

road mileage, 192, 194 

standard road sections, 5 

water-bound macadam, 64, 67 
Wyoming, funds, 193 

motor cars, 195 

oil. 111 

road mileage, 192, 194 



ANNOUNCEMENTS 



21. 



INDEX TO .ANNOUNCEMENTS 

Asphalts and Allied Substances by Herbert Abraham 226 

Asphalts by T. H. Boorman 220 

American Ballast Co 224 

Atlas Portland Cement Co 218 

Barber Asphalt Paving Co., The 217 

Barrett Company, The .219 

Boorman, T. Hugh 220 

Clark, Edward A 220 

Granite Paving Block Manufacturers Assn. of the U. S. A. Inc 222 

Hastings Pavement Co. Inc., The '.223 

Koehring ^Machine Co 225 

New York Mastic Works • • 220 

Robeson Process Co 220 

Societa Sicula per I'esplotazione dell' Asfalto naturale Siciliano. 224 

Spencer, W. B 220 

Union Oil Co. of California 220 

Van Nostrand Co. , D 220, 226 

Willite Road Construction Co. of America, Inc 221 



210 



The Standard of Comparison 
for Paving and Road Materials 

To claim that a paving or road-building material is as good 
as Trinidad or Bermudez asphalt is considered the strongest 
endorsement that can be brought forwaid. 

lUit the materials for which this claim is made are usually 
new and untried, and year after year one ''Just-as-good-as- 
lake-asphalt" follows another into oblivion. 

Bermudez Trinidad 

Road Asphalt Lake Asphalt 

Meanwhile the use of the lake asphalts steadily increases, 
and their position as the standard materials by which all 
others are judged is more firmly fixed (1) by the continued 
good service of natural asphalt roads and pavements, some 
of which, though 30 years old, are in service today; and (2) 
by the duplication of unfortunate experience with artificial 
or manufactured asphalt. 

Engineers and officials with reputations to preserve, and 
taxpayers whose money is to be spent may well consider also 
that even if there w^as any material for paving and road- 
building equaling the lake asphalts in stability, dependability 
and long life, it would take 30 years to prove it. 

THE BARBER ASPHALT PAVING 
COMPANY 

PHILADELPHIA PENNSYLVANIA 



217 



SEND FOR THIS FREE BOOK 




A practical BOOK for engineers, contractors and 
public officials. Obtain j^our copy by writing the 
Service Department of 

The Atlas Portland Cement Company 

Member of Portland Cement Association 

30 Broad St., New York Corn Exchange Bank Bldg., Chicago 

Phila. Boston St. Louis Minneapolis Des Moines Dayton Savannah 



218 



Road Materials, Etc. 

The Barrett Company has a record of forty years in fur- 
nishing paving materials. Its experience and reputation 
gained through the years are coupled with progressiveness. 
Its engineers and chemists are constantly at work on the 
solution of new problems. Each year marks a distinct 
advance. 

Barrett materials combine knowledge and experience. 

"Tar via- X** is u^ed as a binder in the construction of mac. 
adam roads. 

**Tarvia-A** and **Tarvia-B** are used for maintenance on 
many kinds of roads. 

Barrett's Paving Pitch is used as a filler on stone block^ 
wood block and brick paving. Special grades are made to meet 
every requirement and a new mastic filler has been developed for 
use in stone and brick pavements. 

Barrett's Carbosota Creosote Oi7 is designed for preserv- 
ing all timber used in highway fences and bridges. 

Barrett's Ever Jet Paint is a black paint designed for pro- 
tecting exposed ironwork. 

Booklets and particulars on request 

The /^H/iM^ Company 

New York Chicago Philadelphia Boston St. Louis Cleveland 

Cincinnati Pittsburgh Detroit Birmingham 

Kansas City Mirmeapolis Salt Lake Citj Seattle Peoria 

THE BARRETT COMPANY, Limited: Montreal Toronto Winnipeg 

Vancouver St. John. N. B. Halifax, N. S. Sydney. N. S. 



219 




The Literature of 

ROAD MAKING and MAINTENANCE 



On our shelves is the most complete stock of technical, industrial, 
engineering and scientific books in the United States. The technical 
literature of every trade relating to road work is well represented, 
as is every branch of Civil Engineering. 

A large number of these we publish and for an ever increasing 
number we are the sole agents. 

ALL OUR INQUIRIES ARE CHEERFULLY AND CAREFULLY 

ANSWERED AND COMPLETE CATALOGS AS WELL AS 

SPECIAL LISTS ARE SENT FREE ON REQUEST 



D 



25 PARK PLACE 



VAN NOSTRAND COMPANY 
Publishers and Booksellers 



NEW YORK 



UNION OIL COMPANY 
of California 

ASPHALT— ROAD OILS 

Los Angeles San Francisco 
CALIFORNIA 


T. HUGH BOORMAN, C. E. 

Consulting Engineer 

Forti6cations and Military Roads 
City Pavements and Efficiency 
Washington Building, New York City 

W. B. SPENCER, C. E. 

SPECIALIST IN 

ROAD MACHINERY 

30 Church Street New York 


GLUTRIN ROAD BINDER 

Particulars from 

ROBESON PROCESS CO. 

18 East 41st Street 
New York City 


NEW YORK MASTIC WORKS 

Established 1872 

Original Importers of Neuchatel and Seyssel 

Rock Asphalt 

War and Navy Departments 

Specialiijts in Asphalt construction 

T. HUGH BOORMAN, Cons. Eng. 

1 Broadway New York City 


EDWARD A. CLARK 

Mining and Drilling Engineer 

Asphalt, Coal, Manganese and Zinc Properties 
for Sale 

Park Row Building New York City 


ASPHALTS 

1914 Road Edition by 
T. HUGH BOORMAN, C. E. 

Price, $2.00 

W. T. COMSTOCK CO. 

23 Warren Street New York City 



220 



How to Save Transportation Costs 

is the 

Question of the Hour 



Wl LLITE 

TRADE MARK REG. U, S. PAT. OFFICE 



Pavement for Military Roads 
and Country Highways 

Patented U. S. A., July 11, 1916 

The Invention of H. P. WILLIS, B.E., M. Am. Soc. C. E., formerly 

Chief Engineer X. Y. State Highway Department 



Willite has the overwhelming commercial advantage over all other 
types of pavement (which have to pay 100 per cent, of all material entering 
into their construction) because about 85 per cent of all the raw materia] 
(native mineral aggregate), used in both the WILLITPJ foundation and 
WILLITE wearing course costs nothing, as it is obtained right in the road 
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selection, no matter what the character of the soil may be, such as mixed 
earth, sand, gravel, shale, sedimentary sand, disintegrated granite, etc. 



Willite Road Construction Co. 

of America, Inc. 
51 Chambers Street NEW YORK 



221 



THE FIRST COST 
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Improved Granite 
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—The Taxpayer. 



Good Material Well Laid is Absolute Economy 

Granite Paving Block Manufacturers' Ass'n 

of the U. S. A., Inc. 



31 State Street 



Boston, Mass. 



Facts , fiqures and practice 
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Write for^ 
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PERMANENT PAVING" 
AND LATEST 
SPECIFICATIONS 




222 



Asphalt Blocks 

for 

Resurfacing Country Roads 




A REAL PAVEMENT ON A REAL COUNTRY ROAD 

ALBANY POST ROAD, TOWN OF MT. PLEASANT, N. Y. 

LAID 1910 

Part of an Eight Mile Stretch of Asphalt Blocks 

The Asphalt Block is a composition of Trinidad "Lake" Asphalt, crushed trap rock 
and inorganic dust, thoroughly mixed at a temperature of 300°F., and pressed into 
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The manufacture of Asphalt Blocks is now a national industry with plants in 
many parts of the country. The use of Asphalt Blocks has reached a total of 
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Asphalt Block Pavements are Durable, Reasonable in Cost, Pleasing in Ap- 
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Asphalt Blocks have stood the test of time 

For further information address 

THE HASTINGS PAVEMENT CO. 

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22.S 



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Asphaltic Roadway Gravel 
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LIMESTONE 



AMERICAN BALLAST COMPANY 

12161-1219 Holston National Bank Building 

KNOXVILLE TENNESSEE 



Societa Sicula per I'esplotazione dell' 
Asfalto naturale Siciliano 

(Own Mines and Works at Ragusa, Sicily) 

HEAD OFFICE AT PALERMO, VIA GIRGENTI 3 

Cable Address, Rotland, Palermo. A. B. C, 5th Ed., Code used 

Exportation of 

SICILY NATURAL ROCK ASPHALT 
SICILY ASPHALT POWDER IN 50 KILO SACKS 
SICILY ASPHALT MASTIC IN 25 KILO BLOCKS 
COMPRESSED SICILIAN ROCK ASPHALT SLABS 

MANY MILLIONS OF SQUARE METRES IN BERLIN, PARIS, VIENNA 
BUCAREST, GLASGOW; CAIRO, EGYPT, AND ATHENS, .\LSO IN MONTREAL 
(CANADA), AND IN NEW YORK, PHILADELPHIA, BOSTON, NEW ORLEANS 
AND OTHER ATLANTIC PORTS IN THE UNITED STATES HAVE BEEN 
LAID WITH SUCCESS SINCE 1888. 

T. HUGH BOOKMAN, Consulting Engineer 

1 Broadway, New York 



224 



600 Pages 6x9 Cloth Illustrated Postpaid $5.00 

ASPHALTS AND 
ALLIED SUBSTANCES 



Their Occurrence, Mode of Production, 
Uses in the Arts and Methods of Testing 

By HERBERT ABRAHAM 

B.S. of Chemistry, Member A. C.S.,S.C.I.,A.S.T.M.,I.A.T.M. 



CONTENTS 



Part I. General Considerations 



Historical outline, non enclature and classi- 
fication of bituminous substances. Chemistry 
of bituminous substances. Geology and origin 



of bitumens and pyrobitumens. Annual pro- 
duction of asphalts, asphaltites and^asphalti- 
pyrobitumens. 



Part II. Semi-Solid and Solid Native Bituminous Substances 



Methods of refining. Mineral waxes (Ozoker- 
ite, Montan Wax, Hatchettite, etc.) Deposits of 
natural asphalts occurring in a fairly pure state. 
Deposits of natural asphalts associated with 



mineral matter. Asphaltite deposits (Gilsonite 
Glance Pitch and Grahamite). Asphaltic pyro- 
bitumen deposits (Elaterite, Wurtzilite, Albert- 
ite and Impsonite). Pyrobituminous shales. 



Part III. Tars and Pitches 



Methods of producing tars and pitches. Wood- 
tar, wood-tar pitch and rosin pitch ; Peat and 
lignite tars and pitches; Shale tar and shale 
tar pitch; coal tar and coal-tar pitch; oil-gas 



and water gas tars and pitches; Paraffine wax 
and wax tailings; Petroleum asphalts; Wurtzi- 
lite pitch; Fatty-acid pitches and j bone-tar 
pitch. 



Part IV. Manufactured Products and their Uses 



Methods of blending. Bituminous dust-pre- 
ventatives. Bituminous road-surfacings. Bitu- 
minous fillers for stone or concrete pavements. 
Sheet asphalt pavements. Asphalt block pave- 
ments. Impregnated wood block pavements. 
Wood preservatives. Asphalt mastic flooring. 



Bituminous sheet roofings and floor coverings. 
Asphalt shingles. Bituminous waterproofiing 
membranes. Asphalt insulating and sheathing 
papers. Asphalt plastic compounds. Bitumi- 
nous waterproofing, compounds for cement. 
.\sphalt paints, varnishes and japans. 



Part V. Methods of Testing 



Physical characteristics (color, fracture lustre, 
streak, specific gravity, viscosity, hardness, duc- 
tility and tensile strength tests). Heat tests 
(fusing point, volatile matter, flash point, burn- 
ing point, fixed carbon and distillation tests). 
Solubility tests (in carbon bisulphide, carbon 
tetrachloride, petroleum naphtha and other 
solvents). Chemical tests (Water, Carbon, 
Hydrogen, Sulphur, Nitrogen, Free Carbon, 



Naphthalene, Paraffine, Saturated hydrocar- 
bons, Sulphonation Residue, Mineral Matter, 
Saponifiable Constituents, Unsaponifiable Mat- 
ter and G lycerol) . Analysis of Paving Materials. 
Analysis of Asphalt Plastic Compositions, etc. 
Analysis of Sheet Roofings, Shingles, Mem- 
branes, etc. Analysis of Asphalt Paints, Var- 
nishes and Japans. 



D. VAN NOSTRAND COMPANY 



PUBLISHERS AND BOOKSELLERS 



25 Park Place 



New York 



226 



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Neutralizing agent: Magnesium Oxide 
Treatment Date: April 2004 

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